The greatest common factor (GCF) refers to a factor that is COMMON to two or more numbers. You have only one number in the question! The greatest factor of any number, such as 424856, is itself.
The GCF of 18 and 42 is 6. The GCF of 42 and 56 is 14.
The GCF is 4.
The greatest common factor of 42 and 56 is 14.
The GCF is 8.
The GCF of 42, 48, and 78 is 6.