Question 120
A positive integer $n$ is friendly if every pair of neighbouring digits of $n$, written in base 10, differs by exactly 1. For example, $6787$ is friendly, but $211$ and $901$ are not.
Find all odd natural numbers $m$ for which there exists a friendly integer divisible by $64 m$.
Find all odd natural numbers $m$ for which there exists a friendly integer divisible by $64 m$.