Iterated Digit Sums

★ 7/10number theory Modular Arithmetic Estimation

Problem

Let $A = 5555^{5555}$ , let $B$ be the digit sum of $A$ , $C$ the digit sum of $B$ , and $D$ the digit sum of $C$ . Find $D$ .

Answer

Solution

Difficulty	7/10
Topics	number theory, Modular Arithmetic, Estimation

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