在1-20中,奇数有:1,3,5,7,9,11,13,15,17,19;
偶数有:2,4,6,8,10,12,14,16,18,20;
质数有:2,3,5,7,11,13,17,19;
合数有:4,6,8,9,10,12,14,15,16,18,20;
既是奇数又是合数的是9,15;
故答案为:1,3,5,7,9,11,13,15,17,19;2,4,6,8,10,12,14,16,18,20;2,3,5,7,11,13,17,19;4,6,8,9,10,12,14,15,16,18,20;9,15.