This is just idle curiosity but since there are people on this list -=20 most of them - smarter than me, someone probably knows the answer. If a and b are prime numbers, and their product a X b is c, then is c=20 divisible by *only* a and b? Guaranteed? My feeling is that it is but I=20 lack the knowledge of what to search for to find the definitive answer. BTW, this does *not* involve, for me, any sort of cryptography. In other=20 words, I'm not trying to re-invent any crypto ciphers. Thanks! --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .