NumberFormat is an option for NumberForm and related functions that specifies how the mantissa, base, and exponent should be assembled into a final print form.
NumberForm[expr, n] prints with approximate real numbers in expr given to n-digit precision.
NumberMarks is an option for InputForm and related functions that specifies whether ` marks should be included in the printed forms of approximate numbers.
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.
Numerator[expr] gives the numerator of expr.
NumericFunction is an attribute that can be assigned to a symbol f to indicate that f[arg_1, arg_2, ...] should be considered a numeric quantity whenever all the arg_i are ...
NumericQ[expr] gives True if expr is a numeric quantity, and False otherwise.
NyquistGridLines is an option to NyquistPlot that specifies contours of constant magnitude and phase of a closed-loop system.