LARGE numbers

[Tuvas]

I've been thinking about writing a program to generate the world's
largest prime numbers, just for the fun of it. This would require being
able to hold an 8000000 digit number into memory (25 megabits, or a
little over 3 megs of memory for just one variable...) I would also
need several smaller variables. This came about as I optimised a prime
number generator more and more, until I came with the idea to try to
find the largest ever, using python. Any ideas? I'll probably try to
run this on a mainframe eventually, although they might not like it
very much... I'll run it on my home computer to first test it. Anyways,
let me know if there's a way to make python support numbers so high.
Thanks!