Common factors calculator

Find every common factor (common divisor) of two or more numbers. The greatest common factor is highlighted in the list.

Numbers (comma- or space-separated)

Common factors

1, 2, 3, 4, 6, 12

Greatest common factor

Common factor count

Sum of common factors

Each number's factors

How to find common factors

List every factor of each number (every positive integer that divides it cleanly).
Take the intersection of all those lists — values that appear in every list.
The largest value in the intersection is the greatest common factor (GCF).

CommonFactors(a, b, …) = Factors(a) ∩ Factors(b) ∩ …

Equivalently, every common factor of a, b, … is also a factor of their GCF — so the GCF and its divisors give you the complete list.

Is 1 always a common factor?

Yes — 1 divides every integer. Two numbers whose only common factor is 1 are called coprime (or relatively prime).

Can I check more than two numbers?

Yes — enter as many as you like. The intersection still applies.

What's the difference between this and GCF?

This calculator lists every common factor; the GCF calculator reports just the greatest. Every other common factor is a divisor of the GCF.