The One Way to Arrange Nothing When you first learn about factorials, it sounds simple: Pick a number—say 4—and multiply your way down to 1. 4 × 3 × 2 × 1 = 24. That’s 4 factorial, or 4! Factorials don’t just make big numbers—they tell us how many arrangements are possible with distinct elements. 3! = 6, because there are six ways to arrange A, B, and C. Add D, and you can place it in any of four spots for each of those six. That’s 4 × 6 = 24 = 4!. The pattern keeps going: 5! = 5 × 4!, 4! = 4 ×