Suppose the number is abc...z. Let's write N=0.abc...zabc...z.... Therefore, (N+z)/10=0.zabc...zabc...z.... We want this to equal KN, with K an (unknown) integer, 10>K>1. (If K≥10, KN would have more digits than K.) If (N+z)/10=KN, then N=z/(10K-1). As a≥1, then z≥K. So, if we study z/(10K-1) for 10>K>1, z≥K, and look for the smallest abc...z, we'll have the answer. For K=z=4 we produce N=0.102564102564... so the answer is 102564.
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