2016 digits are written on a circle. Reading these digits counterclockwise, starting from a certain number, you get a number divisible by 81. Prove that by reading these digits clockwise, we obtain a number divisible by 81 for every starting number.
Source: Saudi Arabia JBMO training test 1 2019, P1
Tags: number theory
2016 digits are written on a circle. Reading these digits counterclockwise, starting from a certain number, you get a number divisible by 81. Prove that by reading these digits clockwise, we obtain a number divisible by 81 for every starting number.