Click it and let it run. Going to try to make this run faster. Press turbo mode (Shift click on mac or right click on PC). Press the stop sign to stop. This uses an optimised brute force method (instead of checking all the factors it just checks prime factors less than the square root of the current highest prime). Explanation inside.
PRIMES!!! (One is not a prime... some websites still think it is...) Did you know that the 500th prime is 3571? Well if you leave this open for 30 minutes (now down to 0.154 SECONDS OR OVER 1168831% FASTER!!!) you'll know that and a lot more! (Working on speed). Primes up to a million in around four min. Primes up to three million in around thirty five min. Working on making a user friendly version.