content: esCapicua :: Integer -> Bool
  esCapicua n = esAux n 1
  
  
  esAux :: Integer -> Integer -> Bool 
  esAux n k | (cantDigitos n <= k) = True
            | (ultimoDigito n == iesimoDigito n k) && ((cantDigitos n) > k) = esAux (div n 10) (k+1)
            | otherwise = False
  
  
  ---------------------------
  ultimoDigito :: Integer -> Integer
  ultimoDigito n = mod n 10
  
  
  primerDigito :: Integer -> Integer
  primerDigito n = div n (10^((cantDigitos n) - 1))
  
  -----------------------------------------------------------------------------
  
  iesimoDigito :: Integer -> Integer -> Integer
  iesimoDigito n i = mod (div n (10^((cantDigitos n)-i))) 10
  
  cantDigitos :: Integer -> Integer
  cantDigitos n = auxCant n 0 
  
  auxCant :: Integer -> Integer -> Integer
  auxCant n c | mod n 10 == n = c+1
              | otherwise = auxCant (div n 10) (c+1)
  
  
  {-
  34543 -> True
  121 -> True
  1231 -> False 
  2345432 ->  True
  9090909 -> True
  23237873232 -> True 
  126321 -> False
  785087 -> False
  -}