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# Predefined Values

CFNumber provides some predefined number values.

## Topics

### Constants

[`let kCFNumberNaN: CFNumber!`](/documentation/CoreFoundation/kCFNumberNaN)

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

[`let kCFNumberNegativeInfinity: CFNumber!`](/documentation/CoreFoundation/kCFNumberNegativeInfinity)

Designates a negative infinity value.

[`let kCFNumberPositiveInfinity: CFNumber!`](/documentation/CoreFoundation/kCFNumberPositiveInfinity)

Designates a positive infinity value.


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