To calculate the largest prime factor of a number

getLargestFactor.clj

(ns scratch.core)

(defn dividable? [number]
  #(zero? (mod number %))
)

(defn dividableByAny? [number divList]
    (> (count (filter (dividable? number) divList)) 0)
  )

(defn getAllPrimes [number]
    (loop [i 2, list '()]
      (if (<= i number)
        (if (dividableByAny? i list)
            (recur (inc i) list)
            (recur (inc i) (conj list i))
          )
          list
        )
      )
  )


(defn isPrime? [number]
  (let [x  (Math/sqrt number)]
    (not (some (dividable? number) (getAllPrimes x)))
    )
  )


(defn getFactors [number]
  (loop [i 2 x number list '()]
    (let [div? (dividable? x)]
      (if (<= i (Math/sqrt number))
        (if (div? i)
            (do ;(println i (/ x i))
                (recur i (/ x i) (conj list i (/ x i)))
              )
            (recur (inc i) x list)
          )
        list
        )
    )
  )
)

;(getLargestFactor 600851475143)  ;6857
(defn getLargestFactor [number]
    (let [f (getFactors number) bar (if (zero? (count f)) (conj f number) f)]
      (apply max (filter isPrime? bar))
    )
  )