I had a student in my computer class ask me a mathematics question: she asked what was the use of prime numbers? She knew there were lots of work done on primes, but what she wanted to know was, what *good* are they, besides being a fascination to math people. It caught me unawares, I mumbled something about that there are theorems where it is easier to prove them for primes, and then extend the proof to all numbers, but I couldn't think of an example. I looked around a little, but most of the things I see, off-hand, talk about all the things you can prove about primes themselves, not what use they might be elsewhere. I could probably mention mods, since you need mod p to be prime, to allow division. But what I really want is some examples where they might be of use in "everyday life", or at least in some mathematics that would apply to more everyday things. Anyone have ideas of what to tell her? Or references of places I could look? Thanks, -- Stan -- Stan Isaacs 210 East Meadow Drive Palo Alto, CA 94306 stan@isaacs.com