It was calculated using the UBASIC interpreter. Per http://archives.math.utk.edu/software/msdos/number.theory/ubasic/.html, from which (among other places) you can download a copy of this MS-DOS software,
UBASIC is a BASIC-like environment which is suitable for number theoretic investigations. Version 8 of UBASIC has the high precision real and complex arithmetic (up to 2600 digits) of previous versions, but adds exact rational arithmetic and arithmetic of polynomials with complex, rational, or modulo p coefficients, as well as string handling and limited list handling capabilities. In addition UBASIC has context-sensitive on-line documentation (read ubhelp.doc for information). The file ubhelp.xxx that this uses is ASCII and can be printed for hard copy documentation. (from the documentation)
So, if you liked that, then you'll love
?factorial(1000) 4023872600770937735437024339230039857193748642107146325437999104299385123986290
... middle truncated due to limit on what flooble will take as a comment...
96372524230560855903700624271243416909004153690105933983835777939410970027753472
00000000000000000000000000000000000000000000000000000000000000000000000000000000
00000000000000000000000000000000000000000000000000000000000000000000000000000000
00000000000000000000000000000000000000000000000000000000000000000000000000000000
000000000
OK
At 2568 digits it's almost at the limit of UBASIC.

Posted by Charlie on 2003-02-26 08:20:19