102. A certain number is written in the duodecimal system; for which divisor $m$ is the following divisibility rule valid: if the sum of the digits of the number is divisible by $m$, then the number is also divisible by $m$?
102. $m=11$, because $12=11\cdot1+1, \quad 12^{2}=11\cdot13+1$ and so on.