Number Methods - JavaScript Tutorial - w3Schools - Chapter 21 - English

These number methods can be used on all JavaScript numbers:

Method Description
toString() Returns a number as a string
toExponetial() Returns a number written in exponential notation
toFixed() Returns a number written with a number of decimals
toPrecision() Returns a number written with a specified length
ValueOf() Returns a number as a number

Number() Returns a number converted from its argument.
parseFloat() Parses its argument and returns a floating point number
parseInt() Parses its argument and returns a whole number

Number Object Methods
These object methods belong to the Number object:

Method Description
Number Methods Cannot be Used on Variables

The number methods above belong to the JavaScript Number Object.

Using X.isInteger() where X is a variable, will result in an error:

TypeError X.isInteger is not a function.