module PrimeFactors (primeFactors) where

primeFactors :: Integer -> [Integer]
primeFactors 1 = []
primeFactors x = primeFactors' x 2
  where primeFactors' x n
          | x < n = []
          | x `mod` n == 0 && x > n = [n] ++ primeFactors' (x `div` n, n + 1)
          | otherwise = [x]