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. $$\begin{array}{c}3400,\text{-}17,\frac{4}{3},\text{ and }90.835\end{array}$$ 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.