4 times 21 is 84. In symbols: 4 × 21 = 84, and 21 × 4 = 84 too.
4 × 21 means adding 4 to itself 21 times: that is 21 copies of 4, which add up to 84.
4, 8, 12, 16, 20, 24, 28, 32, 36, 40, 44, 48, ... (keep going to the 21th multiple). The 21th multiple of 4 is 84.
4 × 21 = 4 × 20 + 4 × 1 = 80 + 4 = 84.
Halve one number and double the other: 4 × 21 = 2 × 42 = 84.
84 ÷ 4 = 21
84 ÷ 21 = 4
84 is even. Prime factorization: 2 × 2 × 3 × 7.
| Multiplication | Answer |
|---|---|
| 3 × 21 | 63 |
| 5 × 21 | 105 |
| 4 × 20 | 80 |
| 4 × 22 | 88 |
| 4 × 23 | 92 |
| 4 × 19 | 76 |
| 6 × 21 | 126 |
| 2 × 21 | 42 |
See also: factors of 84.
Other numbers? Browse the multiplication table, the squares and cubes or the exponent calculator.