Originally posted by David113Correct.
333333331 = 17 x 19607843
Originally posted by FabianFnasInteresting.
31, 331, 3331, 33331, 333331, 3333331, 33333331 are primes, 333333331 is not.
Once, before computers and mechanical calculators, there was a conjecture that every number started with a number of threes, ending with a one was a prime until, with great effort, 333333331 was factorized, and therefore, the conjecture was disproven.
Originally posted by David113And I thought im geek...
I find this hard to believe, since it is easy to prove - without any computer - that this sequence contains a composite number.
By Fermat's Little Theorem, if p is a prime and x is an integer not divisible by p, then x ^ (p - 1) - 1 is divisible by p.
Let p = 31, x = 10. Then you get the result - 999999999999999999999999999999 (30 9's) is divisible by ...[text shortened]... + 31 = 33333333333333333333333333333331.
so 33333333333333333333333333333331 is not prime.