(define prime? 
  X -> (prime-h? X (isqrt X) 2))

(define isqrt
   X -> (isqrt-help X 1))

(define isqrt-help
   X Y -> Y 			where (= (* Y Y) X)
   X Y -> (- Y 1)			where (> (* Y Y) X)
   X Y -> (isqrt-help X (+ Y 1)))

(define prime-h?
    X Max Div -> true		where (> Div Max)
    X Max Div -> false		where (integer?  (/ X Div))	
    X Max Div -> (prime-h? X Max (+ 1 Div)))