Good day, sean.hinde> > 2^BigNumber mod ReasonableNumber, then there's no need to sean.hinde> > calculate 2^BigNumber. sean.hinde> sean.hinde> Aha! Any pointers on how to do this? Volume 2 of Donald Knuth's "The Art of Computer Programming" is now your best friend. Or search google with "arbitrary precision arithmetic". Best Regards, Vladimir Sekissov