number v. numeral v. digit

A number is the abstract concept of a quantity.

A numeral is a symbol or a group of symbols used to represent a number. The Roman numeral CXXXVII can be expressed more familiarly as one hundred thirty-seven.

A digit is a single character in a numbering system. Decimal uses the digits 0 through 9; binary uses 0 and 1; the 16 hexadecimal digits are 0 through 9, and A, B, C, D, E, and F.

6732 is a 4-digit numeral representing the number six thousand seven hundred thirty-two.