GCF and LCM of 2 and 15

The GCF of 2 and 15 is 1. The LCM of 2 and 15 is 30.

• GCF (greatest common factor, also called GCD or HCF) of 2 and 15 = 1
• LCM (least common multiple) of 2 and 15 = 30

2 and 15 share no common factor except 1, so they are coprime (relatively prime). When two numbers are coprime their LCM is simply their product: 2 × 15 = 30.

Method 1: list the factors (GCF)

Factors of 2: 1, 2.
Factors of 15: 1, 3, 5, 15.
Common factors: 1. The greatest of these is 1.

Method 2: prime factorization

2 = 2 (prime)
15 = 3 × 5

GCF: multiply the prime factors both numbers share: there are none, so the GCF is 1.

LCM: multiply every prime the maximum number of times it appears in either number: 2 × 3 × 5 = 30.

Method 3: Euclidean algorithm (GCF)

Divide the larger number by the smaller and repeat with the remainder until it is 0. The last non-zero remainder is the GCF.

1. 15 = 7 × 2 + 1
2. 2 = 2 × 1 + 0

The last non-zero remainder is 1, so GCF(2, 15) = 1.

LCM by listing multiples

Multiples of 2: 2, 4, 6, 8, 10, 12, 14, 16, 18, ...
Multiples of 15: 15, 30, 45, ...
The first number in both lists is 30.

Check: GCF × LCM = product

1 × 30 = 30 = 2 × 15. This always holds for two numbers, so you can find the LCM as (2 × 15) ÷ 1 = 30.

Simplifying the fraction 2/15

2/15 is already in lowest terms because the GCF of 2 and 15 is 1.

GCF and LCM of similar pairs

See also: factors of 2 · factors of 15 · 2/15 as a decimal.

Different numbers? Use the GCF and LCM calculator (any amount of numbers) or browse all GCF and LCM pairs.