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

LiDIA  
   C++ Library For Computational Number Theory.
   http://www.informatik.tu-darmstadt.de/TI/LiDIA/

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

Maple Worksheets by John Cosgrave  
   A selection of Maple (V.5) worksheets for teaching purposes.
   http://www.spd.dcu.ie/johnbcos/Maple.htm

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/

Implementations of Extended LLL  
   By Wilberd van der Kallen.
   http://www.math.uu.nl/people/vdkallen/lllimplementations.html

giantint  
   Library of routines for large integer arithmetic and number theory.
   http://www.perfsci.com/free/giantint/index.html

MIRACL  
   Multiprecision Integer and Rational Arithmetic C/C++ Library.
   http://indigo.ie/~mscott/

GNU MP Home Page  
   Free library for arbitrary precision arithmetic.
   http://www.swox.com/gmp/

Math Archives Software  
   Mac/Number Theory section.
   http://archives.math.utk.edu/software/mac/numberTheory/.directory.html

FTP Sites, Calculator Programs and Archives  
   In the Number Theory Web.
   http://www.maths.uq.edu.au/~krm/N1.html

GIMPS FAQ list  
   About the Mersenne Prime Freeware.
   http://www.mersenne.org/faq.htm

ECMNET  
   Elliptic curve factoring software.
   http://www.loria.fr/~zimmerma/records/ecmnet.html

Mersenne Prime Freeware  
   Freeware to search for Mersenne Primes. Pointers to FreeLIP, GMP, HFloat, apfloat, CALC.
   http://www.samurai.com/mersenne/freeware.html

HiPiLib - High Performance Libraries  
   Home of PIOLOGIE, a library for arbitrary precision arithmetic, operating on natural, integer and rational numbers.
   http://www.hipilib.de/

Schulenberg and Associates  
   Factoring programs. Windows, free download.
   http://www.schulenberg.com/

CLN - Class Library for Numbers  
   C++ library by Bruno Haible.
   http://www.ginac.de/CLN/

Number-Theoretic Hacks  
   Algorithms implemented by David Eppstein.
   http://www.ics.uci.edu/~eppstein/numth/

Number Field Sieve NET  
   A client/server system for NFSNET by Henrik Olsen.
   http://www.iaeste.dk/~henrik/projects/nfsnet.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

Paul's TI-92 Number Theory Archive  
   Download site for number theory programs adapted from UBASIC/MALM for the TI-92.
   http://www.geocities.com/Hollywood/2979/ntheory.html

Jim Howell Software  
   Large integer arithmetic.
   http://home.netcom.com/~jrhowell/math/software.htm

Java PHASER Project  
   An application for numerically and graphically analyzing dynamical systems.
   http://www.math.miami.edu/~phaser

apfloat  
   High-performance arbitrary precision arithmetic package for C++ and Java.
   http://www.apfloat.org/

SIMATH  
   Computer algebra system for number theoretic applications.
   http://tnt.math.metro-u.ac.jp/simath/

Galois  
   An algebra/number theory package by R. Lidl, R. W. Matthews and R. Wells.
   http://www.riaca.win.tue.nl/archive/can/SystemsOverview/Special/NumberTheory/Galois.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

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

Factorizer  
   A Windows program to find all factors of any positive integer less than 2^31 - 1; decompose numbers into their prime constituents; find prime numbersand pairs of primes; and to plot Erdos-Kac and Palmen Color histograms. Down load free demo, order full v
   http://www.hermetic.ch/factors/factors.htm

MAGMA/PARI Calculator  
   Web interface for short programs in either language.
   http://modular.fas.harvard.edu/calc/

Large Number Arithmetic in BASIC  
   Library for large-integer arithmetic, plus some number theory modules.
   http://www.home.zonnet.nl/vspickelen/Largefiles/LargeInt.htm

Magma Computational Algebra System Home Page  
   A large, well-supported software package for computationally hard problems in algebra, number theory, geometry and combinatorics.
   http://magma.maths.usyd.edu.au/

NZMATH  
   Python based number theory oriented calculation system, developed at Tokyo Metropolitan University. Downloads, mailing list.
   http://tnt.math.metro-u.ac.jp/nzmath/

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

ZEN  
   A toolbox for computation in finite rings, by Florent Chabaud and Reynald Lercier. ANSI-C source, free download, GPL.
   http://fchabaud.free.fr/English/ZEN/

L  
   A C++ class library, datasets and command line program for computing zeros and values of L-functions, by Michael Rubinstein.
   http://pmmac03.math.uwaterloo.ca/~mrubinst/L_function_public/L.html

Kaprekar Series Generator  
   A java application for determining the Kaprekar Constants and Series for numbers in various radixes.
   http://kaprekar.sourceforge.net/

Multiprecision Software Directory  
   Fortran multiprecision software by David H. Bailey of Lawrence Berkeley Lab.
   http://crd.lbl.gov/~dhbailey/mpdist/mpdist.html