'Number Digit' of a number :-

 In Vedic Maths, the Number Digit (ND) of a number is called 'Navasesh' meaning 'nine and its remainder'.

 USES AND APPLICATIONS : This concept is used as a general method of verification in mathematics, to verify various mathematical operations such as addition, subtraction, multiplication and division. But, before we go ahead, here are some important points to remember : The number digit of any non-zero number is always a single-digit non-zero number (obviously, the number digit of zero is always zero). If number is made up of all 9's and /or all sub-additions of 9's, then its number digit is 9. If you encounter any negative number while applying this verification rule to subtraction, convert it to a positive number, by just adding 9 to the negative number (for ex. if your answer is -4, convert it like this : -4 + 9 = 5). While multiplying this verification rule to division, convert the number digit equivalent into a multiplication form and then apply the verification rule. Note : This method of checking is not a foolproof method, but works reasonably well.