mynumber.hs

import GHC.Int

validateMyNumber :: Int64 -> Bool
validateMyNumber myNumber
  | length (show myNumber) <= 12 =
      let (x:pn) = take 12 . map (`mod` 10) . iterate (`div` 10) $ myNumber
          qn     = [if n <= 6 then n + 1 else n - 5 | n <- [1..11]]
          y      = (`mod` 11) . sum . zipWith (*) qn $ pn
      in  x == if y <= 1 then 0 else (11 - y)
  | otherwise = False

main :: IO ()
main = do
    print $ validateMyNumber 123456789010 -- False
    print $ validateMyNumber 123456789011 -- False
    print $ validateMyNumber 123456789012 -- False
    print $ validateMyNumber 123456789013 -- False
    print $ validateMyNumber 123456789014 -- False
    print $ validateMyNumber 123456789015 -- False
    print $ validateMyNumber 123456789016 -- False
    print $ validateMyNumber 123456789017 -- False
    print $ validateMyNumber 123456789018 -- True
    print $ validateMyNumber 123456789019 -- False
    print $ validateMyNumber 023456789013 -- True