Are cheat codes just numbers

Yes, that is essentially what a cheat code is, although some games have letters available for cheat codes. However, everybody on the web appears to think that a cheat CODE is a synonym for CHEAT. This is incredibly wrong. examples:

Cheat: to unlock ????? beat sixty-five enemies in ?????? ??????? mode.

Cheat CODE: to unlock ????? enter 184726402/at the title screen, press up, down ,down ,left, right, down.