### Sum of digits of a number

Some of you may be aware that sum of digits of a number always give the remainder produced when the number is divided by 9.

For example sum of digits of the number 29307634 = 2 + 9 + 3 + 0 + 7 + 6 + 3 + 4 = 34 and again the sum of digits 3 + 4 = 7. So when 2307634 is divided by 9 the remainder will be 7. OK. But is there any proof? Read below.