Task

Take a   Natural Number   in a given base and return the sum of its digits:

   110         sums to   1
   123410   sums to   10
   fe16       sums to   29
   f0e16     sums to   29


(defn sum-digits [n base] 
  (let [number (if-not (string? n) (Long/toString n base) n)]
    (reduce + (map #(Long/valueOf (str %) base) number))))