The GCF of 18 and 27 is 9. The LCM of 18 and 27 is 54.
Factors of 18: 1, 2, 3, 6, 9, 18.
Factors of 27: 1, 3, 9, 27.
Common factors: 1, 3 and 9. The greatest of these is 9.
18 = 2 × 3 × 3
27 = 3 × 3 × 3
GCF: multiply the prime factors both numbers share: 3 × 3 = 9.
LCM: multiply every prime the maximum number of times it appears in either number: 2 × 3 × 3 × 3 = 54.
Divide the larger number by the smaller and repeat with the remainder until it is 0. The last non-zero remainder is the GCF.
The last non-zero remainder is 9, so GCF(18, 27) = 9.
Multiples of 18: 18, 36, 54, 72, ...
Multiples of 27: 27, 54, 81, ...
The first number in both lists is 54.
9 × 54 = 486 = 18 × 27. This always holds for two numbers, so you can find the LCM as (18 × 27) ÷ 9 = 54.
Divide the top and bottom by the GCF 9: 18/27 = 2/3.
| Numbers | GCF | LCM |
|---|---|---|
| 2 and 18 | 2 | 18 |
| 3 and 18 | 3 | 18 |
| 4 and 18 | 2 | 36 |
| 5 and 18 | 1 | 90 |
| 6 and 18 | 6 | 18 |
| 7 and 18 | 1 | 126 |
| 2 and 27 | 1 | 54 |
| 3 and 27 | 3 | 27 |
| 4 and 27 | 1 | 108 |
| 5 and 27 | 1 | 135 |
| 6 and 27 | 3 | 54 |
| 7 and 27 | 1 | 189 |
See also: factors of 18 · factors of 27.
Different numbers? Use the GCF and LCM calculator (any amount of numbers) or browse all GCF and LCM pairs.