Kiriti's number URL: https://brilliant.org/mathematics-problem/kiritis-number/?group=kI5dClibjr16#!/solution-comments/5492/
While reading up the solutions to this question, I discovered that John Aries Lopez comment that 111...(12 times) satisfies the equation and therefore N = 1122334456 which means the digit sum is 31. So isn't the answer suppose to be 31??
But if that is the case, then the divisibility test of 9 is not accurate. 111...(12 times) does not sum up to a value divisible by 9...but it is divisible by 9!