You're using a select subset of many definitions for figure, number, and digit.

A digit is a single numerical value, like the digit **5** in the number **2507**.

A number can have one or more digits, like **7** or **2507** or **2,507.38**.

A figure can be a shape, a diagram, or a number; if used to describe a number, it can be composed of a single digit or of multiple digits.