A number of numbers you should know about

Below are some important sets of numbers that they don't teach about in school but that everyone should know.

Deep numbers. They ahave a second nature. For instance, "pi" and "american pi", or "twelve" and "ocean's twelve".

Big numbers, also called "bignums". They are lists of digits that have many digits. Now if those digits also have lists of digits, you can grow trees with that!
Well, not exactly like that, but you get the idea.

This is an excellent publication about big numbers:

Phone numbers. They're long and have hyphens in the middle. For instance, 1-800-555-1111. The coolest thing about them is that you have your own, so you don't have to envy Euler because of his Euler's number. Don't take too many numbers however, like Fibonacci or Liouville did, cause you won't be able to memorize them.

Hex numbers. Used by witches when they try to cast a hex on someone. Spells are usually hard to memorize and pronounce and if you make a mistake, you can cast the wrong hex! So witches came up with smart a numbering system.

Note that negative numbers have a hyphen at the beginning, phone numbers in the middle, but only hex numbers can have a hyphen at the end, like "C-", commonly used by teachers in schools (all teachers are witches, by the way).

iNumbers. They're a bit like imaginary numbers, but the "i" is on the left. For instance, i386.

1337 numbers. The only 1337 number is 1337, but it's allright for a set to have only one element.

Wikipedia can also teach you about plastic numbers, almost integers and hypertranscendental numbers. Seriously.