1,2,4,5,10,20
20 has six factors.
1, 2, 4, 5, 10, 20 Pick four.
Four common factors.
85 has four factors.
Four, four, six, three, six and two factors respectively.
15, 20, 30, 60
It is 10 whose factors are: 1, 2, 5 and 10
The factors of 20 are 1,2,4,5,10 and 20. Two are odd, four are even.
The two factors of 24 that give you a sum of 20 are 12 and 8.
The other factors could be 4 and 5 or 1 and 20.
Four of them.
5, 10, and 20 are factors of 20 that are not also factors of 12.