An interactive interpreter for big integer and multi-precision floating point arithmetic with a Pascal/Modula like syntax. It has several builtin functions for algorithmic number theory.
A DOS tool to compute aliquot chains with small starting numbers, by Ivo DŁntsch.
A calculator program for doing arbitrary precision integer arithmetic, written in ANSI C and Yacc, with a number of built-in functions for number theory, by Keith Matthews.
Encyclopedia of Integer Sequences Seeker
EIS-Seeker is a libguile-based scheme interpreter devoted to the study of the Encyclopedia of Integer Sequences database. It is intended to help find new relations between sequences. C/Scheme, Posix.
Supports arbitrary precision integer arithmetic calculations with interactive execution: it is a superior version of the basic bc program which comes with the UNIX operating system. Keith Matthews has written several number-theoretic programs.
Java PHASER Project
An application for numerically and graphically analyzing dynamical systems.
KANT / KASH
KANT is a software package for sophisticated computations in number fields and in global function fields. With KASH you are able to use the powerful KANT V4 functions within a shell.
Kaprekar Series Generator
A java application for determining the Kaprekar Constants and Series for numbers in various radixes.
Large Number Arithmetic in BASIC
Library for large-integer arithmetic, plus some number theory modules.
Multiprecision Integer and Rational Arithmetic C/C++ Library.
Maple Worksheets by John Cosgrave
A selection of Maple (V.5) worksheets for teaching purposes.
Math Archives Software
PC/Number Theory section.
NTL: A Library for doing Number Theory
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.
Python based number theory oriented calculation system, developed at Tokyo Metropolitan University. Downloads, mailing list.
Algorithms implemented by David Eppstein.
Computer algebra system for number theoretic applications.
Schulenberg and Associates
Factoring programs. Windows, free download.
High-performance arbitrary precision arithmetic package for C++ and Java.
Portable C++ class for integers with unlimited range, designed to be fast, functional and simple in use.
A Mathematica package by Stany De Smedt.