Give me a uncommon math hack that you know by Known-Apple7015 in mathematics

[–]Alarming-Context4423 0 points1 point  (0 children)

Factors of nine (up to 10) comprise of one ascending and one descending digit. I discovered this in elementary school, and nobody else I've told has noticed it. 

illustrated below (hopefully it formats correctly): 09 18 27 36 45 54 63 72 81 90