A number is a way to represent a value. Most numbers are a combination of digits and symbols. There are many types of numbers, such as integers, fractions, and decimal numbers. $\begin{gathered} 3400, \ \text{-}17, \ \dfrac{4}{3}, \text{ and } \ 90.835 \end{gathered}$ Numbers are constant, which means that their value never changes, unlike variables. Number sets are used to categorize numbers together with other numbers that have similar properties.