Numeric Value: 21
The folowing table expresses '21' in various number bases. 'DRx' shows the result of 'digit reducing' resulting in an X-digit long number.
| Base | DR5 | DR4 | DR3 | DR2 | DR1 |
|---|---|---|---|---|---|
| 2 | 10101 | 11,10 | 1 | ||
| 3 | 210 | 10 | 1 | ||
| 4 | 111 | 3 | |||
| 5 | 41,10 | 1 | |||
| 6 | 33,10 | 1 | |||
| 7 | 30 | 3 | |||
| 8 | 25 | 7 | |||
| 9 | 23 | 5 | |||
| 10 | 21 | 3 | |||
| 11 | 1A,10 | 1 | |||
| 12 | 19 | A | |||
| 13 | 18 | 9 | |||
| 14 | 17 | 8 | |||
| 15 | 16 | 7 | |||
| 16 | 15 | 6 |
Math World
Factors: 3 * 7
21 is the 8th Fibonacci number.
21 is in the Pythagorean Triples: (21, 220, 221), (20, 21, 29).
21 is the sum of the counting numbers from 1 to 6 (See 'The Sum/Product of the First N Counting Numbers').
Physical World
21 is the atomic weight of Scandium (Sc).
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