A single number cannot have a greatest common divisor because "common" refers to factors that two or more numbers have in common. You have only one number.
The Greatest Common Divisor is 4
The Greatest Common Divisor is 28
The Greatest Common Divisor is 4
The Greatest Common Divisor is 35
The Greatest Common Divisor is 1
The Greatest Common Divisor is 2
The Greatest Common Divisor is 22
The Greatest Common Divisor is 9
The Greatest Common Divisor is 19
The Greatest Common Divisor is 10
The Greatest Common Divisor is 13
The greatest common divisor is 45.