The only composites you can eliminate by looking at the low order digits, in any base, are those divisible by the primes dividing the base; and if you supplement with checking that the number is not itself equal to that prime, only the single low order digit need be looked at. Looking at more low order digits lets you determine divisibility by higher powers of the those primes, but not anything really new. Franklin T. Adams-Watters -----Original Message----- From: Henry Baker hbaker1@pipeline.com The operative word here is "intuition". Yes, I did mean low order thingy's -- bits, digits, whatevers. If the low-order decimal digit is 2, 4, 6, 8, 0, then the number is divisible by 2; if the low-order decimal digit is 5, 0, then the number is divisible by 5. If you take a larger number of low-order digits, you can exclude more composites. ___________________________________________________ Try the New Netscape Mail Today! Virtually Spam-Free | More Storage | Import Your Contact List http://mail.netscape.com