15 times 21 is 315. In symbols: 15 × 21 = 315, and 21 × 15 = 315 too.
15 × 21 means adding 15 to itself 21 times: that is 21 copies of 15, which add up to 315.
15, 30, 45, 60, 75, 90, 105, 120, 135, 150, 165, 180, ... (keep going to the 21th multiple). The 21th multiple of 15 is 315.
15 × 21 = 15 × 20 + 15 × 1 = 300 + 15 = 315.
315 ÷ 15 = 21
315 ÷ 21 = 15
315 is odd. Prime factorization: 3 × 3 × 5 × 7.
| Multiplication | Answer |
|---|---|
| 14 × 21 | 294 |
| 16 × 21 | 336 |
| 15 × 20 | 300 |
| 15 × 22 | 330 |
| 15 × 23 | 345 |
| 15 × 19 | 285 |
| 17 × 21 | 357 |
| 13 × 21 | 273 |
Other numbers? Browse the multiplication table, the squares and cubes or the exponent calculator.