There is no answer to this question within the normal context of "factor" and "paired".
1 x 35, 5 x 7, 7 x 5, 35 x 1
5 is not a factor of 57.
5
They are 5 and 7
gcf(35, 63) = 7.
9
5 x 9 = 45
5 x 9 = 45
5 x 9 = 45
It is: 5*12 = 60
A Greatest Common Factor (GCF) is used to compare two or more numbers. A single number cannot have a Greatest Common Factor.