28:
1*28 = 28
2*14 = 28
4*7 = 28
Factors of 28 are 1, 2, 4, 7, 14, 28.
15:
1*15 = 15
3*5 = 15
Factors of 15 are 1, 3, 5, 15.
36:
1*36 = 36
2*18 = 36
3*12 = 36
4*9 = 36
6*6 = 36
Factors of 36 are 1, 2, 3, 4, 6, 9, 12, 18, 36
29:
1*29 = 29
Factors of 29 are 1, 29.