How many mutants are in crash bandicoot?

Depends... technically, Crash is a mutant.

If you're referring to 'Titans', the creatures that you can jack in Mind Over Mutant and Crash of the Titans, there are 12 in CotT.

In MoM, there are 10 basic Titans, 6 'hero' or 'boss' Titans, and at the end you can jack Cortex.