Question

12,20,28,36 are all multiples of 1, 2 and what?

Answer 1

1) one is multiple of all positive integers. So, yes it is multiple of all that numbers.

2) Two is multiple for all those number which has even digit in unit place. So, yes they all are multiple of 2 too.

Answer 2

4 is also a multiple of 12 20 28 36 :P