Largest Product In A Series#

primes = 2 : filter (null . tail . primeFactors) [3,5..]

primeFactors n = factor n primes
  where
    factor n (p:ps) 
        | p*p > n        = [n]
        | n `mod` p == 0 = p : factor (n `div` p) (p:ps)
        | otherwise      =     factor n ps

problem_10 = sum $ takeWhile (<2000000) primes

OUTPUT

142913828922