This number is divided by 7 plus 6, divided by 8 plus 7, and divided by 9 plus 8. It can be concluded that:

This number plus 1 can be divisible by (7*8*9).

So I subtract 1 from 7*8*9 = 504 and get 503. After checking, it really meets the conditions of the problem.

So the conclusion is: any number that meets 7*8*9*n- 1 (n is a positive integer).

Simply put: 504n- 1 (n is a positive integer)