All of them.
3 and 11
1,2,3,5,6,10,12,15,30 Thirty has 9 factors.
The common factors are: 1, 2, 5, 10.
1 , 33 , 3 , 11
The factors of 39 are: 1, 3, 13, 39.
They are: 1, 2, 4, 8, 16 and 32
1 and 5
1,2,3,5,6,30,15,10
1, 2, 3, 5, 6, 10, 15, 30
Numbers which are the factors of thirty and multiples of five are 5, 10, 15 and 30.
A prime number because 31 has only two factors which are itself and one