IT-CESENATICO 1997 Problem 5

Let $X$ be the set of natural numbers whose all digits in the decimal representation are different. For $n \in N$ , denote by $A_n$ the set of numbers whose digits are a permutation of the digits of $n$ , and $d_n$ be the greatest common divisor of the numbers in $A_n$ . (For example, $A_{1120} =\{112,121,...,2101,2110\}$ , so $d_{1120} = 1$ .) Find the maximum possible value of $d_n$ .