Lets factor.
12 | 2
6 | 2
3 | 3
1
So,
12 = 2 . 2 . 3
So we can say: 2 and 3 are factors obviously.
We have 2 . 2 so, 2 . 2 = 4, he's a factor too.
We have 2 . 3 so, 2 . 3 = 6, he's a factor too.
Every number have 1 and himself as his factor.
So, n is {1, 2, 3, 4, 6, 12}