The Number Shark is an educational game to improve the knowledge of factors and prime numbers.
The idea of the Number Shark game is to win as many of the numbers as possible for yourself, so that the sum of your numbers is higher than the sum of the Number Shark, and also to reach the highest possible score. When you choose a number, the Number Shark gets all free real factors (the real factors of the number "6" are "1", "2", and "3").
The Number Shark game playfully teaches the handling with factors and prime numbers and was originally designed for school kids.
Further information can be found in the online help integrated in the game itself.