[Jtsummers]

Not necessarily. The sum of the digits ranges from 36-45, there are 10 possible digits of which 9 will be used. If, say, 5 were the unused number then it would not be divisible by 9.

[lern_too_spel]

You're right. I misread the question. It's 9 of the 10 digits 0-9 instead of all 9 digits 1-9 as in sudoku.

[amyres]

Exactly. The actual solution to the puzzle in question has a GCD not divisible by 9.