This is documentation for Mathematica 8, which was
based on an earlier version of the Wolfram Language.

NumberQ

 NumberQ[expr]gives True if expr is a number, and False otherwise.
NumberQ tests whether an object is explicitly a number:
NumberQ tests whether an object is explicitly a number:
 Out[1]=
 Out[2]=
 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:
The same is true for complex and directed infinities:
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:
NumberQ is equivalent to MatchQ[#, _Integer|_Rational|_Real|_Complex]&:
If NumberQ[x] is True, then NumericQ[x] is also True: