It is: 3
2. 12 = 2 * 2 * 3
6
12 is a multiple of 2.
Only if the number is a multiple of 12.
2 is the only number is that both a factor of 2 and a multiple of 2.
1, 2, 3, 4, 8
6 is a factor of 30 and a multiple of 2.
2
1, 2, 3, 4, 6, 12
12
2 is a factor of 14 but not a multiple of 7.