---
title: kCFNumberNaN
framework: corefoundation
role: symbol
role_heading: Global Variable
path: corefoundation/kcfnumbernan
---

# kCFNumberNaN

“Not a Number.” This value is often the result of an invalid operation, such as the square-root of a negative number.

## Declaration

```swift
let kCFNumberNaN: CFNumber!
```

## See Also

### Constants

- [kCFNumberNegativeInfinity](corefoundation/kcfnumbernegativeinfinity.md)
- [kCFNumberPositiveInfinity](corefoundation/kcfnumberpositiveinfinity.md)