1, 2 and 4
Since 36 is a factor of 72, all of its factors are common and all less than 200. Common multiples in that range are 72 and 144.
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 200 and 205 are: 1 and 5
81 and 200 have no common prime factors.
The common factors of 36 and 63 are 1, 3 and 9
The common factors of 36 and 80 are: 1, 2, and 4
The common factors of 36 and 81 are: 1, 3, and 9
The common factors of 36 and 99 are: 1, 3, 9