Don't run to long because as it finds more and more prime numbers the next prime number will be harder and harder to find. This means no matter how strong your computer is you will eventually crash. So don't run the program to long.
My comment: There's no danger of computer crash because the program does one calculation after another as long as you want. The project will maybe stop when Scratch recognizes a maximum of possible list items. I slimmed down the code to make the program work significantly faster.
