My favourite numbers.

11 is the largest known multiplicative persistence.
12 is the smallest abundant number.
9 is the maximum number of cubes that are needed to sum to any positive integer.
31 is a Mersenne prime.
17 is the number of wallpaper groups.
2 is the only even prime.
3 is the number of spatial dimensions we live in.

You can find the whole list at Stetson.edu.