ProjectEuler Problem 3 - Largest prime factor

The prime factors of 13195 are 5, 7, 13 and 29.

What is the largest prime factor of the number 600851475143 ?

A function that returns list of factors:

factors n = factors' n 2 where factors' n p | n == 1 = [] | mod n p == 0 = p:factors' (div n p) p | otherwise = factors' n (p + 1)

The largest prime factor of 600851475143 is:

maximum $ factors 600851475143

in Python