A New Primal Screen

Quick, is 91 prime or composite? OK, you have that one, but how about 12345678910111213? As with 91, the answer is still relatively easy to find, since this 17-digit number is divisible by the smallish prime 113, and so it is composite. But searching for factors often gets bogged down, and when a large number really is prime, a factor search is a terrible way to proceed.