A square number is a number that you get when you multiply a whole number by itself. For example, if you take the number 3 and multiply it by 3, you get 9, which is a square number. The first few square numbers are 1, 4, 9, 16, and 25. These numbers can be visualized as squares, where the length of each side is the whole number. Square numbers have many interesting properties. For instance, the difference between two consecutive square numbers is always an odd number. This means that if you look at the square numbers 1, 4, 9, and 16, the differences are 3, 5, and 7, which are all odd. Understanding square numbers is important