21 times 21 is 441. In symbols: 21 × 21 = 441 (21 squared).
21 × 21 means adding 21 to itself 21 times: that is 21 copies of 21, which add up to 441.
21, 42, 63, 84, 105, 126, 147, 168, 189, 210, 231, 252, ... (keep going to the 21th multiple). The 21th multiple of 21 is 441.
21 × 21 = 21 × 20 + 21 × 1 = 420 + 21 = 441.
441 ÷ 21 = 21
441 is odd and a perfect square. Prime factorization: 3 × 3 × 7 × 7.
| Multiplication | Answer |
|---|---|
| 20 × 21 | 420 |
| 21 × 22 | 462 |
| 21 × 23 | 483 |
| 19 × 21 | 399 |
See also: 21 squared.
Other numbers? Browse the multiplication table, the squares and cubes or the exponent calculator.