MathDB
Mediocre numbers

Source: Canada Repêchage 2015/3

June 18, 2016
number theorypermutationsAverage

Problem Statement

Let NN be a 3-digit number with three distinct non-zero digits. We say that NN is mediocre if it has the property that when all six 3-digit permutations of NN are written down, the average is NN. For example, N=481N = 481 is mediocre, since it is the average of {418,481,148,184,814,841}\{418, 481, 148, 184, 814, 841\}.
Determine the largest mediocre number.