> For the complete documentation index, see [llms.txt](https://trizen.gitbook.io/sidef-lang/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://trizen.gitbook.io/sidef-lang/programming_tasks/a/arithmetic/rational.md).

# Rational

Sidef has built-in support for rational numbers.

```ruby
for n in (1 .. 2**19) {
    var frac = 0

    n.divisors.each {|d|
        frac += 1/d
    }

    if (frac.is_int) {
        say "Sum of reciprocal divisors of #{n} = #{frac} exactly #{
            frac == 2 ? '- perfect!' : ''
        }"
    }
}
```

## Output:

```
Sum of reciprocal divisors of 1 = 1 exactly 
Sum of reciprocal divisors of 6 = 2 exactly - perfect!
Sum of reciprocal divisors of 28 = 2 exactly - perfect!
Sum of reciprocal divisors of 120 = 3 exactly 
Sum of reciprocal divisors of 496 = 2 exactly - perfect!
Sum of reciprocal divisors of 672 = 3 exactly 
Sum of reciprocal divisors of 8128 = 2 exactly - perfect!
Sum of reciprocal divisors of 30240 = 4 exactly 
Sum of reciprocal divisors of 32760 = 4 exactly 
Sum of reciprocal divisors of 523776 = 3 exactly
```