(defn isDivisible
  "Returns true if num is divisible by div"
  [num div]
  (= 0 (mod num div)))

(defn isPrime
  "Checks if a number is a prime or not"
  [n]
  (if (or (and (> n 2) (isDivisible n 2)) (<= n 1))
    false
    (loop [i 3 top (int (Math/sqrt n))]
    (do
      (if (> i top)
      true
      (if (isDivisible n i)
        false
        (recur (+ i 2) top)))))))