There cannot be a greatest common factor if there are not at least two numbers to compare. The greatest common factor is the largest factor that all the numbers have in common - the largest factor that they all share.
The greatest common factor is 28.
The greatest common factor of 16 and 28 is 4
The greatest common factor of 28 and 20 is 4.
The Greatest Common Factor of 28, 48 is 4.
The greatest common factor of 48 and 28 is 4.
The greatest common factor of 7 and 28 is 7.
The greatest common factor of 28 and 120 is 4.
The greatest common factor of 28 and 250 is 2.
The greatest common factor of 154 , 28 = 14
The greatest common factor of 2702 , 28 = 14
The greatest common factor of 28 and 55 is 1
The greatest, and only, common factor of 57 (=3x19) and 28 (=22x7) is 1.