diff --git a/.travis.yml b/.travis.yml
index bdef7bf..f9d09e0 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,6 +1,6 @@
 language: rust
 rust:
-  - 1.36.0
+  - 1.56.0
   - stable
   - beta
   - nightly
diff --git a/Cargo.toml b/Cargo.toml
index bed64f5..f46cae7 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -12,6 +12,8 @@ license = "MIT/Apache-2.0"
 name = "num-bigint-dig"
 repository = "https://github.com/dignifiedquire/num-bigint"
 version = "0.7.0"
+edition = "2021"
+rust-version = "1.56"
 readme = "README.md"
 build = "build.rs"
 autobenches = false
diff --git a/README.md b/README.md
index 503b18e..6011ab6 100644
--- a/README.md
+++ b/README.md
@@ -2,7 +2,7 @@
 
 [![crate](https://img.shields.io/crates/v/num-bigint-dig.svg)](https://crates.io/crates/num-bigint-dig)
 [![documentation](https://docs.rs/num-bigint-dig/badge.svg)](https://docs.rs/num-bigint-dig)
-![minimum rustc 1.36](https://img.shields.io/badge/rustc-1.36+-red.svg)
+![minimum rustc 1.56](https://img.shields.io/badge/rustc-1.56+-red.svg)
 [![Travis status](https://travis-ci.org/dignifiedquire/num-bigint.svg?branch=master)](https://travis-ci.org/dignifiedquire/num-bigint)
 
 Big integer types for Rust, `BigInt` and `BigUint`.
@@ -50,7 +50,7 @@ Release notes are available in [RELEASES.md](RELEASES.md).
 
 ## Compatibility
 
-The `num-bigint` crate is tested for rustc 1.36 and greater.
+The `num-bigint` crate is tested for rustc 1.56 and greater.
 
 ## Alternatives
 
@@ -59,8 +59,8 @@ crates may offer better performance with different trade-offs.  The following
 table offers a brief comparison to a few alternatives.
 
 | Crate                | License        | Min rustc | Implementation |
-| :------------------- | :------------- | :-------- | :------------- |
-| **`num-bigint-dig`** | MIT/Apache-2.0 | 1.36      | pure rust |
+| :------------------- | :------------- |:----------| :------------- |
+| **`num-bigint-dig`** | MIT/Apache-2.0 | 1.56      | pure rust |
 | [`num-bigint`]       | MIT/Apache-2.0 | 1.15      | pure rust |
 | [`ramp`]             | Apache-2.0     | nightly   | rust and inline assembly |
 | [`rug`]              | LGPL-3.0+      | 1.18      | bundles [GMP] via [`gmp-mpfr-sys`] |
diff --git a/src/algorithms/gcd.rs b/src/algorithms/gcd.rs
index a4ae75a..cf6d724 100644
--- a/src/algorithms/gcd.rs
+++ b/src/algorithms/gcd.rs
@@ -2,7 +2,7 @@ use crate::big_digit::{BigDigit, DoubleBigDigit, BITS};
 use crate::bigint::Sign::*;
 use crate::bigint::{BigInt, ToBigInt};
 use crate::biguint::{BigUint, IntDigits};
-use integer::Integer;
+use crate::integer::Integer;
 use num_traits::{One, Signed, Zero};
 use alloc::borrow::Cow;
 use core::ops::Neg;
diff --git a/src/algorithms/jacobi.rs b/src/algorithms/jacobi.rs
index 75f3c7c..327d11a 100644
--- a/src/algorithms/jacobi.rs
+++ b/src/algorithms/jacobi.rs
@@ -1,4 +1,4 @@
-use integer::Integer;
+use crate::integer::Integer;
 use num_traits::{One, Signed, Zero};
 
 use crate::BigInt;
diff --git a/src/algorithms/mod_inverse.rs b/src/algorithms/mod_inverse.rs
index b028133..775504f 100644
--- a/src/algorithms/mod_inverse.rs
+++ b/src/algorithms/mod_inverse.rs
@@ -28,7 +28,7 @@ pub fn mod_inverse(g: Cow<BigUint>, n: Cow<BigUint>) -> Option<BigInt> {
 mod tests {
     use super::*;
 
-    use integer::Integer;
+    use crate::integer::Integer;
     use num_traits::FromPrimitive;
 
     use crate::traits::ModInverse;
diff --git a/src/bigint.rs b/src/bigint.rs
index 9252464..218ffad 100644
--- a/src/bigint.rs
+++ b/src/bigint.rs
@@ -23,7 +23,7 @@ use serde;
 #[cfg(feature = "zeroize")]
 use zeroize::Zeroize;
 
-use integer::{Integer, Roots};
+use crate::integer::{Integer, Roots};
 use num_traits::{
     CheckedAdd, CheckedDiv, CheckedMul, CheckedSub, FromPrimitive, Num, One, Pow, Signed,
     ToPrimitive, Zero,
@@ -32,14 +32,14 @@ use num_traits::{
 use self::Sign::{Minus, NoSign, Plus};
 use super::ParseBigIntError;
 use super::VEC_SIZE;
-use big_digit::{self, BigDigit, DoubleBigDigit};
-use biguint;
-use biguint::to_str_radix_reversed;
-use biguint::{BigUint, IntDigits};
+use crate::big_digit::{self, BigDigit, DoubleBigDigit};
+use crate::biguint;
+use crate::biguint::to_str_radix_reversed;
+use crate::biguint::{BigUint, IntDigits};
 use smallvec::SmallVec;
 
-use IsizePromotion;
-use UsizePromotion;
+use crate::IsizePromotion;
+use crate::UsizePromotion;
 
 use crate::algorithms::{extended_gcd, mod_inverse};
 use crate::biguint::IntoBigUint;
diff --git a/src/bigrand.rs b/src/bigrand.rs
index c0c155a..e71bd0d 100644
--- a/src/bigrand.rs
+++ b/src/bigrand.rs
@@ -4,13 +4,13 @@ use rand::distributions::uniform::{SampleBorrow, SampleUniform, UniformSampler};
 use rand::prelude::*;
 use rand::Rng;
 
-use BigInt;
-use BigUint;
-use Sign::*;
+use crate::BigInt;
+use crate::BigUint;
+use crate::Sign::*;
 
-use big_digit::BigDigit;
-use bigint::{into_magnitude, magnitude};
-use integer::Integer;
+use crate::big_digit::BigDigit;
+use crate::bigint::{into_magnitude, magnitude};
+use crate::integer::Integer;
 #[cfg(feature = "prime")]
 use num_iter::range_step;
 use num_traits::Zero;
@@ -183,7 +183,6 @@ pub struct UniformBigInt {
 impl UniformSampler for UniformBigInt {
     type X = BigInt;
 
-    #[inline]
     #[inline]
     fn new<B1, B2>(low_b: B1, high_b: B2) -> Self
     where
diff --git a/src/biguint.rs b/src/biguint.rs
index c89f90f..521fb55 100644
--- a/src/biguint.rs
+++ b/src/biguint.rs
@@ -61,16 +61,16 @@ fn exp(a: f64) -> f64 {
     libm::exp(a)
 }
 
-use integer::{Integer, Roots};
+use crate::integer::{Integer, Roots};
 use num_traits::float::FloatCore;
 use num_traits::{
     CheckedAdd, CheckedDiv, CheckedMul, CheckedSub, FromPrimitive, Num, One, Pow, ToPrimitive,
     Unsigned, Zero,
 };
 
-use BigInt;
+use crate::BigInt;
 
-use big_digit::{self, BigDigit};
+use crate::big_digit::{self, BigDigit};
 
 use smallvec::SmallVec;
 
@@ -86,8 +86,8 @@ use crate::algorithms::{div_rem, div_rem_digit, mac_with_carry, mul3, scalar_mul
 use crate::algorithms::{extended_gcd, mod_inverse};
 use crate::traits::{ExtendedGcd, ModInverse};
 
-use ParseBigIntError;
-use UsizePromotion;
+use crate::ParseBigIntError;
+use crate::UsizePromotion;
 
 /// A big unsigned integer type.
 #[derive(Clone, Debug)]
diff --git a/src/lib.rs b/src/lib.rs
index a9efa60..550a22b 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -79,52 +79,33 @@
 //!
 //! ## Compatibility
 //!
-//! The `num-bigint` crate is tested for rustc 1.15 and greater.
+//! The `num-bigint-dig` crate is tested for rustc 1.56 and greater.
 //!
 //! ## `no_std` compatibility
 //!
-//! This crate is compatible with `no_std` environments from Rust 1.36. Note
-//! however that it still requires the `alloc` crate, so the user should ensure
-//! that they set a `global_allocator`.
+//! This crate is compatible with `no_std` environments.
+//!
+//! Note however that it still requires the `alloc` crate, so the user should
+//! ensure that they set a `global_allocator`.
 //!
 //! To use in no_std environment, add the crate as such in your `Cargo.toml`
 //! file:
 //!
 //! ```toml
 //! [dependencies]
-//! num-bigint = { version = "0.3", default-features=false }
+//! num-bigint-dig = { version = "0.8", default-features=false }
 //! ```
 //!
 //! Every features should be compatible with no_std environment, so feel free to
 //! add features like `prime`, `i128`, etc...
 
 #![doc(html_root_url = "https://docs.rs/num-bigint/0.2")]
-#![cfg_attr(not(feature = "std"), no_std)]
+#![no_std]
 
-#[cfg(not(feature = "std"))]
-#[macro_use]
 extern crate alloc;
 
 #[cfg(feature = "std")]
-use std as alloc;
-
-#[cfg(feature = "std")]
-extern crate core;
-
-#[cfg(feature = "rand")]
-extern crate rand;
-#[cfg(all(test, feature = "rand"))]
-extern crate rand_chacha;
-#[cfg(all(test, feature = "rand"))]
-extern crate rand_isaac;
-#[cfg(all(test, feature = "rand"))]
-extern crate rand_xorshift;
-
-#[cfg(feature = "serde")]
-extern crate serde;
-
-#[cfg(feature = "zeroize")]
-extern crate zeroize;
+extern crate std;
 
 #[macro_use]
 extern crate smallvec;
@@ -134,17 +115,10 @@ extern crate smallvec;
 extern crate lazy_static;
 
 extern crate num_integer as integer;
-extern crate num_iter;
-extern crate num_traits;
-
-#[cfg(feature = "prime")]
-extern crate byteorder;
-
-extern crate libm;
 
+use core::fmt;
 #[cfg(feature = "std")]
 use std::error::Error;
-use core::fmt;
 
 #[macro_use]
 mod macros;
@@ -158,7 +132,7 @@ pub mod prime;
 pub mod algorithms;
 pub mod traits;
 
-pub use traits::*;
+pub use crate::traits::*;
 
 #[cfg(feature = "rand")]
 mod bigrand;
@@ -186,7 +160,7 @@ enum BigIntErrorKind {
 
 impl ParseBigIntError {
     fn __description(&self) -> &str {
-        use BigIntErrorKind::*;
+        use crate::BigIntErrorKind::*;
         match self.kind {
             Empty => "cannot parse integer from empty string",
             InvalidDigit => "invalid digit found in string",
@@ -219,18 +193,18 @@ impl Error for ParseBigIntError {
     }
 }
 
-pub use biguint::BigUint;
-pub use biguint::IntoBigUint;
-pub use biguint::ToBigUint;
+pub use crate::biguint::BigUint;
+pub use crate::biguint::IntoBigUint;
+pub use crate::biguint::ToBigUint;
 
-pub use bigint::negate_sign;
-pub use bigint::BigInt;
-pub use bigint::IntoBigInt;
-pub use bigint::Sign;
-pub use bigint::ToBigInt;
+pub use crate::bigint::negate_sign;
+pub use crate::bigint::BigInt;
+pub use crate::bigint::IntoBigInt;
+pub use crate::bigint::Sign;
+pub use crate::bigint::ToBigInt;
 
 #[cfg(feature = "rand")]
-pub use bigrand::{RandBigInt, RandomBits, UniformBigInt, UniformBigUint};
+pub use crate::bigrand::{RandBigInt, RandomBits, UniformBigInt, UniformBigUint};
 
 #[cfg(feature = "prime")]
 pub use bigrand::RandPrime;
diff --git a/src/monty.rs b/src/monty.rs
index 3066ace..e63324c 100644
--- a/src/monty.rs
+++ b/src/monty.rs
@@ -4,8 +4,8 @@ use num_traits::{One, Zero};
 use core::ops::Shl;
 use alloc::vec::Vec;
 
-use big_digit::{self, BigDigit, DoubleBigDigit, SignedDoubleBigDigit};
-use biguint::BigUint;
+use crate::big_digit::{self, BigDigit, DoubleBigDigit, SignedDoubleBigDigit};
+use crate::biguint::BigUint;
 
 struct MontyReducer {
     n0inv: BigDigit,
diff --git a/tests/bigint.rs b/tests/bigint.rs
index 550b506..2228883 100644
--- a/tests/bigint.rs
+++ b/tests/bigint.rs
@@ -4,9 +4,9 @@ extern crate num_traits;
 #[cfg(feature = "rand")]
 extern crate rand;
 
-use num_bigint::BigUint;
-use num_bigint::Sign::{Minus, NoSign, Plus};
-use num_bigint::{BigInt, ToBigInt};
+use crate::num_bigint::BigUint;
+use crate::num_bigint::Sign::{Minus, NoSign, Plus};
+use crate::num_bigint::{BigInt, ToBigInt};
 
 use std::cmp::Ordering::{Equal, Greater, Less};
 use std::collections::hash_map::RandomState;
@@ -24,7 +24,7 @@ use num_traits::float::FloatCore;
 use num_traits::{FromPrimitive, Num, One, Pow, Signed, ToPrimitive, Zero};
 
 mod consts;
-use consts::*;
+use crate::consts::*;
 
 #[macro_use]
 mod macros;
diff --git a/tests/bigint_bitwise.rs b/tests/bigint_bitwise.rs
index bec4aa0..82b9fea 100644
--- a/tests/bigint_bitwise.rs
+++ b/tests/bigint_bitwise.rs
@@ -1,7 +1,7 @@
 extern crate num_bigint_dig as num_bigint;
 extern crate num_traits;
 
-use num_bigint::{BigInt, Sign, ToBigInt};
+use crate::num_bigint::{BigInt, Sign, ToBigInt};
 use num_traits::ToPrimitive;
 use std::{i32, i64, u32};
 
@@ -11,7 +11,7 @@ enum ValueVec {
     M(&'static [u32]),
 }
 
-use ValueVec::*;
+use crate::ValueVec::*;
 
 impl ToBigInt for ValueVec {
     fn to_bigint(&self) -> Option<BigInt> {
diff --git a/tests/bigint_scalar.rs b/tests/bigint_scalar.rs
index 86fd449..f0f32bb 100644
--- a/tests/bigint_scalar.rs
+++ b/tests/bigint_scalar.rs
@@ -1,14 +1,14 @@
 extern crate num_bigint_dig as num_bigint;
 extern crate num_traits;
 
-use num_bigint::BigInt;
-use num_bigint::Sign::Plus;
+use crate::num_bigint::BigInt;
+use crate::num_bigint::Sign::Plus;
 use num_traits::{Signed, ToPrimitive, Zero};
 
 use std::ops::Neg;
 
 mod consts;
-use consts::*;
+use crate::consts::*;
 
 #[macro_use]
 mod macros;
diff --git a/tests/biguint.rs b/tests/biguint.rs
index 41c5c3b..f52ee22 100644
--- a/tests/biguint.rs
+++ b/tests/biguint.rs
@@ -3,9 +3,9 @@ extern crate num_integer;
 extern crate num_traits;
 extern crate smallvec;
 
-use num_bigint::Sign::Plus;
-use num_bigint::{BigInt, ToBigInt};
-use num_bigint::{BigUint, ToBigUint};
+use crate::num_bigint::Sign::Plus;
+use crate::num_bigint::{BigInt, ToBigInt};
+use crate::num_bigint::{BigUint, ToBigUint};
 use num_integer::Integer;
 
 use std::cmp::Ordering::{Equal, Greater, Less};
@@ -27,7 +27,7 @@ use num_traits::{
 use num_traits::float::FloatCore;
 
 mod consts;
-use consts::*;
+use crate::consts::*;
 
 #[macro_use]
 mod macros;
@@ -143,7 +143,7 @@ fn hash<T: Hash>(x: &T) -> u64 {
 
 #[test]
 fn test_hash() {
-    use hash;
+    use crate::hash;
 
     let a = BigUint::new(vec![]);
     let b = BigUint::new(vec![0]);
diff --git a/tests/biguint_scalar.rs b/tests/biguint_scalar.rs
index 1e8e899..e25c208 100644
--- a/tests/biguint_scalar.rs
+++ b/tests/biguint_scalar.rs
@@ -1,11 +1,11 @@
 extern crate num_bigint_dig as num_bigint;
 extern crate num_traits;
 
-use num_bigint::BigUint;
+use crate::num_bigint::BigUint;
 use num_traits::{ToPrimitive, Zero};
 
 mod consts;
-use consts::*;
+use crate::consts::*;
 
 #[macro_use]
 mod macros;
diff --git a/tests/modpow.rs b/tests/modpow.rs
index d26b1e6..5479906 100644
--- a/tests/modpow.rs
+++ b/tests/modpow.rs
@@ -57,7 +57,7 @@ static BIG_R: &'static str = "\
                               109c4735_6e7db425_7b5d74c7_0b709508";
 
 mod biguint {
-    use num_bigint::BigUint;
+    use crate::num_bigint::BigUint;
     use num_integer::Integer;
     use num_traits::Num;
 
@@ -100,7 +100,7 @@ mod biguint {
 }
 
 mod bigint {
-    use num_bigint::BigInt;
+    use crate::num_bigint::BigInt;
     use num_integer::Integer;
     use num_traits::{Num, One, Signed, Zero};
 
diff --git a/tests/rand.rs b/tests/rand.rs
index 3c692e5..be6123a 100644
--- a/tests/rand.rs
+++ b/tests/rand.rs
@@ -8,7 +8,7 @@ extern crate rand_isaac;
 extern crate rand_xorshift;
 
 mod biguint {
-    use num_bigint::{BigUint, RandBigInt, RandomBits};
+    use crate::num_bigint::{BigUint, RandBigInt, RandomBits};
     use num_traits::Zero;
     use rand::distributions::Uniform;
     use rand::{Rng, SeedableRng};
@@ -222,7 +222,7 @@ mod biguint {
 }
 
 mod bigint {
-    use num_bigint::{BigInt, RandBigInt, RandomBits};
+    use crate::num_bigint::{BigInt, RandBigInt, RandomBits};
     use num_traits::Zero;
     use rand::distributions::Uniform;
     use rand::{Rng, SeedableRng};
diff --git a/tests/roots.rs b/tests/roots.rs
index d22772e..7be9703 100644
--- a/tests/roots.rs
+++ b/tests/roots.rs
@@ -6,7 +6,7 @@ extern crate num_traits;
 extern crate rand;
 
 mod biguint {
-    use num_bigint::BigUint;
+    use crate::num_bigint::BigUint;
     use num_traits::{One, Pow, Zero};
     use std::{i32, u32};
 
@@ -115,7 +115,7 @@ mod biguint {
             rand::rngs::StdRng::seed_from_u64(4)
         }
 
-        use num_bigint::RandBigInt;
+        use crate::num_bigint::RandBigInt;
         use rand::distributions::Uniform;
         use rand::Rng;
 
@@ -150,7 +150,7 @@ mod biguint {
 }
 
 mod bigint {
-    use num_bigint::BigInt;
+    use crate::num_bigint::BigInt;
     use num_traits::{Pow, Signed};
 
     fn check(x: i64, n: u32) {
diff --git a/tests/serde.rs b/tests/serde.rs
index 11fa335..8b54658 100644
--- a/tests/serde.rs
+++ b/tests/serde.rs
@@ -10,7 +10,7 @@ extern crate num_bigint_dig as num_bigint;
 extern crate num_traits;
 extern crate serde_test;
 
-use num_bigint::{BigInt, BigUint};
+use crate::num_bigint::{BigInt, BigUint};
 use num_traits::{One, Zero};
 use serde_test::{assert_tokens, Token};
 
diff --git a/tests/torture.rs b/tests/torture.rs
index b6f6f5b..a38dbf8 100644
--- a/tests/torture.rs
+++ b/tests/torture.rs
@@ -4,7 +4,7 @@ extern crate num_bigint_dig as num_bigint;
 extern crate num_traits;
 extern crate rand;
 
-use num_bigint::RandBigInt;
+use crate::num_bigint::RandBigInt;
 use num_traits::Zero;
 use rand::prelude::*;