turn on turbo mode (shift click green flag) and the program will find prime numbers. unfortunately, as it goes on, it will go slower, as there will be more prime numbers to check against, and primes will be more scarce. (also, for some inexplicable reason, it runs faster while you See Inside).
math is fun! :) also, I just fixed it so that it goes super fast using the theorem that all composite numbers have a prime factor less than their square root.(credit to proofwiki.org) made the testing more accurate using modulus as opposed to rounding