num-bigint 0.2.6

Big integer implementation for Rust


crate documentation minimum rustc 1.15 Travis status

Big integer types for Rust, BigInt and BigUint.


Add this to your Cargo.toml:

num-bigint = "0.2"

and this to your crate root:

extern crate num_bigint;


The std crate feature is mandatory and enabled by default. If you depend on num-bigint with default-features = false, you must manually enable the std feature yourself. In the future, we hope to support #![no_std] with the alloc crate when std is not enabled.

Implementations for i128 and u128 are only available with Rust 1.26 and later. The build script automatically detects this, but you can make it mandatory by enabling the i128 crate feature.

Random Generation

num-bigint supports the generation of random big integers when the rand feature is enabled. To enable it include rand as

rand = "0.5"
num-bigint = { version = "0.2", features = ["rand"] }

Note that you must use the version of rand that num-bigint is compatible with: 0.5.


Release notes are available in


The num-bigint crate is tested for rustc 1.15 and greater.


While num-bigint strives for good performance in pure Rust code, other 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 MIT/Apache-2.0 1.15 pure rust
ramp Apache-2.0 nightly rust and inline assembly
rug LGPL-3.0+ 1.31 bundles GMP via gmp-mpfr-sys
rust-gmp MIT stable? links to GMP
apint MIT/Apache-2.0 1.26 pure rust (unfinished)