Feed Septimus the Space Monster primes, and primes alone! Click on numbers that are not prime to stop them from reaching him, for they are poison to him. If you click on a prime number, you are forced to return to earth as the Space Monster goes into a rage. See how far you can go. As time goes on, the numbers get larger and more difficult to factor, arrive more quickly, and move more quickly across the screen. Players with a score over 100 beware!

If you can achieve a score of 120 or above, post a video of your feat on YouTube and we will include you and your video on the leaderboard. Let us know at support@bigprimes.org. Ravi Fernando was the first to break 120, with a score of 1004. We have since updated the game to make it scale differently so that the game becomes even more difficult past a score of 100.