digit sum

== English == === Noun === digit sum (plural digit sums) (mathematics, of a positive integer) The sum of all digits. (mathematics, of a positive integer) the number obtained when repeatedly applying above described operation until arriving at a single-digit number. The digit sum of 517 is 4, since 5 + 1 + 7 = 13 and 1 + 3 = 4. ==== Usage notes ==== Those sources that hold to the first definition may refer to the second concept as the iterated digit sum, repeated digit sum or digital root. ==== Translations ====