Cute little project. Primes are a lot of fun to play with.

When you count through your for loop, you don't need to compare any even numbers (after 2), so you can increment by 2 which should double your program's speed.

If a number is not prime, it will have factors that are prime, so if you want to get a lot more advanced and a lot faster, you can keep a table of all the primes you've already computed and iterate through those instead of testing every odd number every time. That gets into a programming technique called "dynamic programming".