Which number is a factor of 20 but not a multiple of four
5, 10, 1, 2, 20, that your factors, there are probably more but those I know off that up of my head
1&20
2&10
5&4
I think they are the only factors of 20 but I could be wrong so the first and second '1&20 and 2&10' should be the answer :)