ARIBAS

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.

http://www.mathematik.uni-muenchen.de/~forster/sw/aribas.html

Aliquot

A DOS tool to compute aliquot chains with small starting numbers, by Ivo Düntsch.

http://archives.math.utk.edu/software/msdos/dynamics/aliquot/.html

CALC

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.

http://www.numbertheory.org/calc/krm_calc.html

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.

http://sourceforge.net/projects/eisseeker

GNUBC

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.

http://www.numbertheory.org/gnubc/gnubc.html

Java PHASER Project

An application for numerically and graphically analyzing dynamical systems.

http://www.math.miami.edu/~phaser

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.

http://www.math.tu-berlin.de/~kant/kash.html

Kaprekar Series Generator

A java application for determining the Kaprekar Constants and Series for numbers in various radixes.

http://kaprekar.sourceforge.net/

Large Number Arithmetic in BASIC

Library for large-integer arithmetic, plus some number theory modules.

http://largeint.sourceforge.net/

MIRACL

Multiprecision Integer and Rational Arithmetic C/C++ Library.

http://indigo.ie/~mscott/

Maple Worksheets by John Cosgrave

A selection of Maple (V.5) worksheets for teaching purposes.

http://www.spd.dcu.ie/johnbcos/Maple.htm

Math Archives Software

PC/Number Theory section.

http://archives.math.utk.edu/software/msdos/number.theory

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.

http://www.shoup.net/ntl/

NZMATH

Python based number theory oriented calculation system, developed at Tokyo Metropolitan University. Downloads, mailing list.

http://tnt.math.se.tmu.ac.jp/nzmath/

Number-Theoretic Hacks

Algorithms implemented by David Eppstein.

http://www.ics.uci.edu/~eppstein/numth/

SIMATH

Computer algebra system for number theoretic applications.

http://tnt.math.se.tmu.ac.jp/simath/

Schulenberg and Associates

Factoring programs. Windows, free download.

http://www.schulenberg.com/

apfloat

High-performance arbitrary precision arithmetic package for C++ and Java.

http://www.apfloat.org/

cBigNumber

Portable C++ class for integers with unlimited range, designed to be fast, functional and simple in use.

http://www.imach.uran.ru/cbignum/