18 times 21 is 378. In symbols: 18 × 21 = 378, and 21 × 18 = 378 too.
18 × 21 means adding 18 to itself 21 times: that is 21 copies of 18, which add up to 378.
18, 36, 54, 72, 90, 108, 126, 144, 162, 180, 198, 216, ... (keep going to the 21th multiple). The 21th multiple of 18 is 378.
18 × 21 = 18 × 20 + 18 × 1 = 360 + 18 = 378.
Halve one number and double the other: 18 × 21 = 9 × 42 = 378.
378 ÷ 18 = 21
378 ÷ 21 = 18
378 is even. Prime factorization: 2 × 3 × 3 × 3 × 7.
| Multiplication | Answer |
|---|---|
| 17 × 21 | 357 |
| 19 × 21 | 399 |
| 18 × 20 | 360 |
| 18 × 22 | 396 |
| 18 × 23 | 414 |
| 18 × 19 | 342 |
| 20 × 21 | 420 |
| 16 × 21 | 336 |
Other numbers? Browse the multiplication table, the squares and cubes or the exponent calculator.