What is a multiple of 9?

A multiple of 9 is a number that can be divided evenly by 9. The first few multiples of 9 are: 9, 18, 27, 36, 45, 54, 63, 72, 81, 90, 99, 108, and so on. The digit sum of any multiple of 9 will always be a multiple of 9. For example, 27 is a multiple of 9, and 2 + 7 = 9, which is also a multiple of 9. Similarly, 81 is a multiple of 9, and 8 + 1 = 9, which is also a multiple of 9. Multiples of 9 are commonly used in mathematics and can be found in various mathematical equations and problems.