It is not possible to give a sensible answer to this question. 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 GCF of 18 and 36 is 18.
The GCF is 18.
The GCF is 18.
It would be 18.
The GCF is 18.
The GCF is 6.
The GCF is 18.
The GCF is 18.
The GCF is 18.
The GCF is 18.
The GCF is 18.
The GCF is 2.