The number 9 is full of surprising tricks! If you multiply 9 by any whole number, then add the digits of the answer together, you’ll always end up with 9 (or a multiple of 9 that adds to 9). For example, 9 × 7 = 63, and 6 + 3 = 9. Or 9 × 12 = 108, and 1 + 0 + 8 = 9. It’s like the number 9 leaves a secret clue in every answer, making it one of the most fascinating numbers in math.