Interesting fact:

Mathematics has its own mysterious tricks. Number 7 is considered to be the most popular number. It’s unique because you can’t multiply or divide it and preserve it in a group. Number 9 is quite the opposite. It’s the most magical number. Why? If you multiply a number by 9 and then add all the digits of the final number, the sum will always be 9. Magic! And have you ever heard that 100 is, in fact, 120? The word’s origin dates back to the word “hundrath” which meant 120. Unbelievable!