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GCF for 3, 5 and 15

"Greatest Common Factor of 3 Numbers" Calculator

What's the Greatest Common Factor (GCF) of 3, 5 and 15?

Answer

GCF of 3, 5 and 15 is

1

Common factors: 1

Only 1 divides all three: no prime is a factor of each of 3, 5 and 15.

Pairs do share factors — GCF(3, 15) = 3, GCF(5, 15) = 5 — just none greater than 1 common to all three.

3 — prime

5 — prime

15 = 3 × 5

Prime	3	5	15	Lowest power
3	3	—	3	—
5	—	5	5	—

— = power 0: the prime is not a factor of this number, so it cannot be in the GCF.

GCF = 1

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See Also

Least Common Multiple of 3 Numbers - Find the Least Common Multiple (LCM) of three numbers
Greatest Common Factor - Find the Greatest Common Factor (GCF) of two numbers
Least Common Multiple - Find the Least Common Multiple (LCM) of two numbers

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What is the GCF of 3, 5 and 15? The GCF of 3, 5 and 15 is 1 — the largest number that divides all three with no remainder. Step-by-step solution for three numbers.

https://calculat.io/en/number/greatest-common-factor-of-3-numbers/3--5--15/generated.jpg

GCF Table

1st	2nd	3rd	GCF
1	3	5	1
2	3	5	1
3	3	5	1
3	4	5	1
3	5	5	1
3	5	6	1
3	5	7	1
3	5	8	1
3	5	9	1
3	5	10	1
3	5	11	1
3	5	12	1
3	5	13	1
3	5	14	1
3	5	15	1
3	5	16	1
3	5	17	1
3	5	18	1
3	5	19	1
3	5	20	1
3	5	21	1
3	5	22	1
3	5	23	1
3	5	24	1
3	5	25	1
3	5	26	1
3	5	27	1
3	5	28	1
3	5	29	1
3	5	30	1

FAQ

What's the Greatest Common Factor (GCF) of 3, 5 and 15?

GCF of 3, 5 and 15 is 1

What prime factors do 3, 5 and 15 share?

None at all: 3, 5 and 15 have no prime factor in common, so the only positive integer dividing all three is 1 and their GCF is 1.

Can you get the GCF of 3, 5 and 15 two numbers at a time?

Yes. The GCF of 3 and 5 is 1, and the GCF of 1 and 15 is 1 — the same answer, because the greatest common factor is associative and does not depend on the order of the three numbers.

How does the GCF simplify the ratio 3 : 5 : 15?

Divide every term by the GCF 1: 3 ÷ 1 = 3, 5 ÷ 1 = 5 and 15 ÷ 1 = 15. So 3 : 5 : 15 in lowest terms is 3 : 5 : 15, and no whole number other than 1 divides all three of those.