Check if a number is Prime

-- Check if a number is Prime
-- source: https://hackersandevelopers.wordpress.com/2017/08/04/bases-matematicas-de-la-criptografia-asimetrica-1/

isPrime x = not $ elem 0 [mod x n | n <- [2..x]]


main = if isPrime 31 then print "It's a prime number"
                     else print "It's not a prime number"