(define (divides? a b) (= (remainder b a) 0))

(define (smallest-divisor n)
  (define (find-divisor test-divisor)
    (cond ((> (square test-divisor) n) n)
          ((divides? test-divisor n) test-divisor)
          (else (find-divisor (+ test-divisor 1)))))
  (find-divisor 2))

; 1 ]=> (smallest-divisor 199)
; 
; ;Value: 199
; 
; 1 ]=> (smallest-divisor 1999)
; 
; ;Value: 1999
; 
; 1 ]=> (smallest-divisor 19999)
; 
; ;Value: 7