奇数：21,23,25,27,29,31,33,35,37,39,41,43,45,47,49,
偶数：22,24,26,28,30,32,34,36,38,40,42,44,46,48,50
素数,23,29,31,37,41,43,47,
合数：21,22,24,25,26,27,28,30,32,33,34,35,36,38,39,40,42,44,45,46,48.49,50,