The sum of digits is a mathematical concept in which the digits of a number are added together to create a new number. This is a widely used method in various areas of mathematics and can be very useful when performing certain calculations or checking numbers for certain properties.

Calculating the sum of digits is quite simple and can be done manually or using an algorithm. For example, if you want to calculate the sum of digits of the number 1234, simply add the individual digits of the number: 1 2 3 4 = 10. The sum of digits of 1234 is therefore 10.

In practice, calculating the sum of digits can be used for a variety of purposes. For example, it can be used to check whether a number is divisible by 9 (if its sum of digits is divisible by 9, then the original number is also divisible by 9), or to detect errors in handwritten numbers (e.g. in bookkeeping or when filling in forms).

Calculating the sum of digits is a simple but powerful tool in mathematics that is used in many different contexts.