I am thinking of a fifty-digit number divisible by 239, of which, each digit is the same, except the ones digit. What is the ones digit?

If for some reason 11111111111111111111111111111111111111111111111110 mod 239 didn't equal 0, you wouldn't need to check the number 2222222....0, 33333.......0, etc. because 239 is prime, and therefore no number can be added an integer amount of times to eliminate the remainder. So therefore, you only need to check 11111111111111111111111111111111111111111111111110 mod 239.

Posted by Justin on 2005-05-13 21:18:35