# NumberQ

NumberQ[expr]

gives True if expr is a number, and False otherwise.

# Details # Examples

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## Basic Examples(1)

NumberQ tests whether an object is explicitly a number:

## Scope(3)

The expression must be manifestly a number:

You can test if a quantity represents a number with NumericQ:

On numerical coercion with N, such quantities generally become numbers:

gives False:

The same is true for complex and directed infinities: NumberQ[Overflow[]] and NumberQ[Underflow[]] give True:  They are both treated as Real:

## Applications(2)

Test if a matrix consists entirely of numbers:

Define a function that only evaluates when the argument is a number:

It does not evaluate with a symbolic argument:

It does evaluate when the argument is a number:

Use FindRoot to find all the solutions of the boundary value problem with :

Plot the solutions:

## Properties & Relations(2)

NumberQ is equivalent to MatchQ[#,_Integer|_Rational|_Real|_Complex]&:

If NumberQ[x] is True, then NumericQ[x] is also True: