ARIBAS is an interactive interpreter for big integer arithmetic and
multi-precision floating point arithmetic with a Pascal/Modula like
syntax. It has several builtin functions for algorithmic number
theory like gcd, Jacobi symbol, Rabin probabilistic prime test,
continued fraction and quadratic sieve factorization, Pollard rho
factorization, etc.

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