frey@garden:~/lein$ cat euler003.clj
#!/usr/bin/clojure

(defn divisible? [a b] (= 0 (mod a b)))

(defn sqrt-rounded-up [x] (inc (int (Math/sqrt x))))

(defn potential-divisors [n] (range (sqrt-rounded-up n) 1 -1))

(defn divisors [n] (filter (fn [x] (divisible? n x)) (potential-divisors n)))

(defn vector-or [coll] (reduce (fn [a b] (or a b)) false coll))

(defn divisible-by-any? [n divisors] (vector-or (map (fn [divisor] (divisible? n divisor)) divisors)))

(defn prime? [n] (not (divisible-by-any? n (potential-divisors n))))

(println (apply max (filter prime? (divisors 600851475143))))