Formula for prime numbers?

Question

Mathematics

I wrote a program where it was necessary to determine a prime number with a minimum amount of code, they suggested a formula: if 2**n%n ==2 then the number is prime, where ** is exponentiation, and% is the remainder of the division, can someone tell me what lies at the base of the formula? (would like to understand how it works)

Answer 1

And the point is, how will you raise at least a million to a power, usually the easiest way is to have a ready-made matrix of prime numbers, then there will be only one line of comparison in code