I would expect that there is no way to know the probability since we do not yet have a knoweldge of all the prime numbers, nor do we have a formula to cumpute the next number... whether this is correct or not, I dont think ANYONE knows... Rhombus wrote: > Take any prime number P.What is the probability that P-1 is divisible > by 6 ?Is the answer really 1/2 ? Jan Vermeylen -- Tim Brierley brierley@erols.com