MPIR is an open source multiprecision integer library derived from version 4.2.1 of the GMP (GNU Multi Precision) project (which was licensed LGPL v2+).

MPIR is constructed by a developer and vendor friendly community of professional and amateur mathematicians, computer scientists and hobbyists.

muParser is an extensible high performance math parser library written in C++. It works by transforming a mathematical expression into bytecode and precalculating constant parts of the expression.

A C++ Library for Parsing Expressions with Strings, Complex Numbers, Vectors, Matrices and more.

programs for computing automorphism groups of graphs and digraphs

NTL is a high-performance, portable C++ library providing data structures and algorithms for manipulating signed, arbitrary length integers, and for vectors, matrices, and polynomials over the integers and over finite fields.

PARI/GP is a computer algebra system designed for fast computations in number theory (factorizations, algebraic number theory, elliptic curves), but also contains a large number of other useful functions to compute with mathematical entities such as matrices, polynomials, power series, algebraic numbers etc., and a lot of transcendental functions.