# Na N Constant

Use Na N in Calcul.io. See what this built-in constant represents, enter it in an editable calculation, and review related values and units.

## NaN

Try it yourself:

```calculio
NaN
0 / 0
```

---

## NaN: not a number

**NaN** represents an invalid or undefined numeric result. It can arise from failed parsing or undefined arithmetic.

## Handling NaN

Test it with [isNaN()](https://calcul.io/function/isNaN/index.md), reject exceptional values with [isFinite()](https://calcul.io/function/isFinite/index.md), and validate type with [isNumeric()](https://calcul.io/function/isNumeric/index.md). Use [nullish()](https://calcul.io/function/nullish/index.md) only for missing values, not every invalid number.

## Caveat

Do not identify NaN with ordinary equality; use the dedicated predicate.

[All constants](https://calcul.io/constants/index.md)