The senary numeral system (also known as base-6 or heximal) has six as its base. It has been adopted independently by a small number of cultures. Like decimal, it is a semiprime, though being the product of the only two consecutive numbers that are both prime (2 and 3) it has a high degree of mathematical properties for its size. As six is a superior highly composite number, many of the arguments made in favor of the duodecimal system also apply to this base-6.
| senary (base 6) | base 21 | senary (base 6) | base 21 |
|---|---|---|---|
| 1 | = 1 | 15 | = b |
| 2 | = 2 | 20 | = c |
| 3 | = 3 | 21 | = d |
| 4 | = 4 | 22 | = e |
| 5 | = 5 | 23 | = f |
| 10 | = 6 | 24 | = g |
| 11 | = 7 | 25 | = h |
| 12 | = 8 | 30 | = i |
| 13 | = 9 | 31 | = j |
| 14 | = a | 32 | = k |
| base 21 | senary (base 6) | base 21 | senary (base 6) |
|---|---|---|---|
| 1 | ≈ 1 | b | ≈ 15 |
| 2 | ≈ 2 | c | ≈ 20 |
| 3 | ≈ 3 | d | ≈ 21 |
| 4 | ≈ 4 | e | ≈ 22 |
| 5 | ≈ 5 | f | ≈ 23 |
| 6 | ≈ 10 | g | ≈ 24 |
| 7 | ≈ 11 | h | ≈ 25 |
| 8 | ≈ 12 | i | ≈ 30 |
| 9 | ≈ 13 | j | ≈ 31 |
| a | ≈ 14 | k | ≈ 32 |
| senary (base 6) | base 21 |
|---|---|
| 1 | = 1 |
| 2 | = 2 |
| 3 | = 3 |
| 4 | = 4 |
| 5 | = 5 |
| 10 | = 6 |
| 11 | = 7 |
| 12 | = 8 |
| 13 | = 9 |
| 14 | = a |