NumberMarks is an option for InputForm and related functions that specifies whether ` marks should be included in the printed forms of approximate numbers.
NumberMultiplier is an option for NumberForm and related functions which gives the string to use as a multiplication sign in scientific notation.
Number
(Built-in Mathematica Symbol) Number represents an exact integer or an approximate real number in Read.
NumberPadding is an option for NumberForm and related functions which gives strings to use as padding on the left- and right-hand sides of numbers.
NumberPoint is an option for NumberForm and related functions which gives the string to use as a decimal point.
NumberQ
(Built-in Mathematica Symbol) NumberQ[expr] gives True if expr is a number, and False otherwise.
NumberSeparator is an option for NumberForm and related functions which gives the string to insert at breaks between digits.
NumberSigns is an option for NumberForm and related functions which gives strings to use as signs for negative and positive numbers.
NumberString represents the characters of a number in StringExpression.
Numerator[expr] gives the numerator of expr.