Mathematicians does things which seems to be impossible. (An example would be the factorial function. Its definition was only defined for positive integers but then mathematicians gave a definition which allowed us to apply the function to any number.)
My question is kind of same. We have defined primes using the integers but can we extend the idea of primes for any number? (It will be like asking that what are the prime factors of $e$).
And if mathematicians have extended the idea of primes then please tell me