A prime number is a whole number greater than 1 with exactly two factors: 1 and itself
Check whether the number is greater than 1
Check divisibility by 2
If the number is 2, it is prime
If the number is even and greater than 2, it is not prime
Test divisibility by odd numbers starting from 3
Stop testing at the square root of the number
If any tested number divides it evenly, it is not prime
If no tested number divides it evenly, it is prime