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MathNet 2010 — Part 04 Question 108

Math Olympiad Vault · MathNet 2010 — Part 04

Question 108

Find all the positive integer $N$ such that there exists $M$ satisfying the following two conditions:

a. $M$'s first few digits coincide with $N$.

b. Let $S$ be a number obtained from $M$ by transferring the digits that express $N$ from the beginning of $M$ to the end of $M$. Then $S \cdot N = M$.

(For example, $M = 460100021743857360295716$ satisfies the conditions, for $N = 46$).