While we are typically accustomed to thinking of the exclamation mark as a purely grammatical tool, it also has a function in mathematics. It is used to denote a concept called a 'factorial.' The factorial of 4, for example, is written "4!" This means that we multiply all the integers leading up to it that are greater than 1.
The factorial of 4, for example is 4 x 3 x 2. It equals 24. The factorial of 5, on the other hand, is 120, since it involves the multiplication of 5 x 4 x 3 x 2. Strictly speaking, the factorial does involve the multiplication of a number by all numbers leading up to it that are greater than zero, and this, of course, includes 1; however, since multiplying that number by one simply gives us the number we already have by the time we get to one, it may seem somewhat superfluous to include 1 in our multiplication. For example, we can multiply For example, if we multiply the factorial of 4, we get 4 x 3 x 2 x 1, which equals 24. By the time we multiply 4 x 3 x 2, we already have 24, and when we multiply this product by 1, we get the same thing.