  ## Encyclopedia > Senary

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# Senary

"Senary" refers to the base-6 numeral system.

All prime numbers besides 2 and 3 end in either 1 or 5.

``` 2,3,5,11,15,21,25,31,35,45,51,101,105,111,115,125,....
```

All known perfect numbers besides 6 itself end in 44.

Base 6 can be counted on hands by using each hand as a digit (0 to 5).

The senary number 3333 is equal to decimal 777.

### Fractions

Six is the product of the first two prime numbers and is adjacent to the next two prime numbers. This makes many senary fractions simple.

``` Decimal   Senary
1/2     1/2   =  0.3
1/3     1/3   =  0.2
1/4     1/4   =  0.13
1/5     1/5   =  0.1111 recurring
1/6     1/10  =  0.1
1/7     1/11  =  0.05050505 recurring
1/8     1/12  =  0.043
1/9     1/13  =  0.04
1/10    1/14  =  0.03333 recurring
```

```   1/12    1/20  =  0.03
1/14    1/22  =  0.023232323 recurring
1/15    1/23  =  0.022222222 recurring
1/16    1/24  =  0.0213
```

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