NumberQ

True only for an explicit numeric literal — a symbolic constant like Pi is NOT NumberQ.

✓ checked against that system · ! checked, with disagreements (hover a chip)Wolfram LanguageNumberQ!↗

NumberQ(expr)True for an Integer/Real/Rational/Complex literal, False otherwise

Typed signatures

Type	Package	Applies
(any) -> boolean	combinatorics	always

Domain: Collections

Details

• Unlike compute-engine's own isNumber (True for Pi, GoldenRatio, …), NumberQ(Pi) is False — Wolfram's own distinction, kernel-checked (NumberQ[Pi] is False, NumberQ[N[Pi]] is True).

Examples

Basic #

live ↗

In$\mathrm{NumberQ}(2)$Out$\mathrm{True}$

Scope #

live ↗

In$\mathrm{NumberQ}(π)$Out$\mathrm{False}$

live ↗

In$\mathrm{NumberQ}(x)$Out$\mathrm{False}$

A numerically evaluated constant is a number

live ↗

In$\mathrm{NumberQ}(N(\sqrt{2}))$Out$\mathrm{True}$

Undefined symbols are not numbers

live ↗

In$\bigl\lbrack\mathrm{NumberQ}(c), \mathrm{NumberQ}(d)\bigr\rbrack$Out$\bigl\lbrack\mathrm{False}, \mathrm{False}\bigr\rbrack$

Two more unknown symbols, both False

live ↗

In$\bigl\lbrack\mathrm{NumberQ}(o), \mathrm{NumberQ}(u)\bigr\rbrack$Out$\bigl\lbrack\mathrm{False}, \mathrm{False}\bigr\rbrack$

live ↗

In$\mathrm{NumberQ}(\sqrt{2})$Out$\mathrm{True}$

live ↗

In$\mathrm{NumberQ}(∞)$Out$\mathrm{True}$

About

Examples	8
Checked against	Wolfram Language 6 agree2 differ
Crosswalk	Wolfram Language

See also: ReIm