1 2 3 6 7 14 21 42质数有 2 3 7 合数有6 14 21 42 既是奇数又是合数的21
42:1,2,3,6,7,12,14,21,42 质数:2,3,7 合数:6,12,14,21,42 奇数:1,3,7,21 偶数:2,6,12,14,42
1.2.3.6.7.14.21.42 2.3.76.14.21.4221