Project Euler #3 in Common Lisp

3.lisp

;;;;
;;;;    3.lisp
;;;;    ProjectEuler
;;;;
;;;;    Created by bitdewy on 4/9/13.
;;;;    Copyright (c) 2013 bitdewy. All rights reserved.
;;;;

;; Project Euler #3
(defun factorization (number)
  (do ((sequence nil) (max (isqrt number)) (i 2 (+ 1 i)))
    ((or (> i number) (> i max)) sequence)
    (do ()
      ((< 0 (mod number i)) sequence)
      (setf number (/ number i))
      (push i sequence))))

(first (factorization 600851475143))