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Mathematica Teacher's Edition

Built-in Functions

Programming

Tests

NumberQ

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

NumberQ[expr] returns False unless expr is manifestly a number (i.e., has head Complex, Integer, Rational or Real).
NumberQ[Infinity] gives False.
NumberQ[Overflow[ ]] and NumberQ[Underflow[ ]] give True.
See The Mathematica Book on the web: Section 2.3.5 and Section 3.1.1.
See also: NumericQ, IntegerQ, TrueQ, Complexes.

Further Examples