The greatest common factor (GCF) or greatest common divisor (GCD) of a single number, such as 20, doesn't really apply in the same way it does when comparing two or more numbers. Instead, if you want to consider the factors of 20, they are:
- 1
- 2
- 4
- 5
- 10
- 20
If you have another number you'd like to find the GCF with in relation to 20, please provide it, and I can help you find the GCF!