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I know that if we want the last 10 decimal digits of $$1234^{1234^{1234}}$$ we should compute $1234^{1234^{1234} \bmod\ \phi(10^{10})} \bmod 10^{10}$ to keep the exponent small. And that technically, $1234^{1234^{1234}\ \bmod\ 10^{10}} \bmod 10^{10}$ is incorrect. Yet they are equal. Why?

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    What do you mean by "why"?2012-10-26
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    I mean why are they equal for these particular constants even though the approach, in general, is flawed. Is this an artifact of base 10? Does 1234 have a particular property? Or does this always work for any base and any constant?2012-10-26

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