The GCF of 16 and 40 is 8. The LCM of 16 and 40 is 80.
Factors of 16: 1, 2, 4, 8, 16.
Factors of 40: 1, 2, 4, 5, 8, 10, 20, 40.
Common factors: 1, 2, 4 and 8. The greatest of these is 8.
16 = 2 × 2 × 2 × 2
40 = 2 × 2 × 2 × 5
GCF: multiply the prime factors both numbers share: 2 × 2 × 2 = 8.
LCM: multiply every prime the maximum number of times it appears in either number: 2 × 2 × 2 × 2 × 5 = 80.
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 8, so GCF(16, 40) = 8.
Multiples of 16: 16, 32, 48, 64, 80, 96, ...
Multiples of 40: 40, 80, 120, ...
The first number in both lists is 80.
8 × 80 = 640 = 16 × 40. This always holds for two numbers, so you can find the LCM as (16 × 40) ÷ 8 = 80.
Divide the top and bottom by the GCF 8: 16/40 = 2/5.
| Numbers | GCF | LCM |
|---|---|---|
| 2 and 16 | 2 | 16 |
| 3 and 16 | 1 | 48 |
| 4 and 16 | 4 | 16 |
| 5 and 16 | 1 | 80 |
| 6 and 16 | 2 | 48 |
| 7 and 16 | 1 | 112 |
| 2 and 40 | 2 | 40 |
| 3 and 40 | 1 | 120 |
| 4 and 40 | 4 | 40 |
| 5 and 40 | 5 | 40 |
| 6 and 40 | 2 | 120 |
| 7 and 40 | 1 | 280 |
See also: factors of 16 · factors of 40.
Different numbers? Use the GCF and LCM calculator (any amount of numbers) or browse all GCF and LCM pairs.