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Thread: phi(n)=2^31

  1. #1
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    Post phi(n)=2^31

    Find an odd number n with phi(n)=2^31.

    Thank you very much.
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  2. #2
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    Quote Originally Posted by Jenny20 View Post
    Find an odd number n with phi(n)=2^31.

    Thank you very much.
    $\displaystyle n=2^{31}+1$
    This is a Mersenne Prime.
    And its phi function is 1 less.
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    I got a different question for you.
    Find a number such that,
    $\displaystyle \phi(n)=31^2$
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    hi perfecthacker,

    Please do teach me. I do not know how to get it backward for the n.

    If you ask me what is phi(6912) , then I can easily tell you that is 2304. But if you give me an answer and ask me to get back to n, i have no idea how to get it.
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  5. #5
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    Quote Originally Posted by Jenny20 View Post
    hi perfecthacker,

    Please do teach me. I do not know how to get it backward for the n.

    If you ask me what is phi(6912) , then I can easily tell you that is 2304. But if you give me an answer and ask me to get back to n, i have no idea how to get it.
    My question was a trick question. Because,
    $\displaystyle \phi(n)$ is always even for $\displaystyle n>1$.
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