If you remember, there is a divisibility rule of 9 that it would divide any number if the sum of digits of the number add up to one of its multiples. So here,
Now, it may be any number that would add up to make a multiple of 9. So, 2 could be one number which would add up to 9 which is, of course, a multiple of 9. So, * can be replaced by 2 and the number thus becomes 522.