Check whether the number is less than 2
If it is less than 2, it is not prime
If it is 2, it is prime
If it is greater than 2 and even, it is not prime
Test whether it is divisible by any integer from 3 up to the square root of the number
If any divisor divides it evenly, it is not prime
If no divisor divides it evenly, it is prime