The factors of 20 are:
1, 2, 4, 5, 10, 20
The factors of 36 are:
1, 2, 3, 4, 6, 9, 12, 18, 36
The common factors are:
1, 2, 4
1 and 2
Common factors of 18 and 20 are: 1 and 2.
1 and 2 are factors common to 6 and 20
1 and 5
It is: 180
1, 2 and 4
The common factors of 18 and 36 are 18,9,6,3,2,1.
The common factors of 27 and 36 are 1, 3 and 9.
The common factors of 36 and 40 are 1,2 and 4.
Since 12 is a factor of 36, all of the factors of 12 are common to 36.
The common factors of 21 and 36 are 1 and 3
The common factors of 36 and 63 are 1, 3 and 9