The answer is simply three.
The Greatest Common Factor of 21, 24, 14: 1
the greatest common factor for 21 and 24 is 3.
The highest common factor of 21 and 24 is 3.
The greatest commonfactor(gcf) of 24 and 21 is 3
The Greatest Common Factor (GCF) is: 3
The greatest factor common to both 21 and 24 is 3.
The GCF is 3.
The GCF of 21, 24, and 36 is 3.
The GCF is 3.
The GCF is 1.
The GCF is 3.
The GCF is: 3