Prove Euler's Totient Function: Divisibility of phi((2^n)-1) by n

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In summary, the conversation discusses Euler's totient function and its relation to the problem of proving n|phi((2^n)-1). The hint suggests computing o[2] in U_((2^n)-1) and using the fact that phi(k) is an even integer for any k. The conversation also explores the relationship between phi((2^n)-1) and U_((2^n)-1), as well as the relationship between o[g] and the order of a finite group G.
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Homework Statement


Let phi denote Euler's totient function, ie for k in N, phi(k) is the number of natural numbers less than k which are relatively prime to k.
Prove that for every n in N we have n| phi((2^n) -1).
(Hint: Compute o[2] in U_(2^n)-1, the group of units in Z mod (2^n)-1)


The Attempt at a Solution


I understand that in the hint, o[2]=n...but I don't know how to relate it to the problem.

I also found that the value of phi(k) for any k is an even integer.
 
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How does phi((2^n)-1) relate to U_((2^n)-1)? I.e. what sort of numbers in {0, ..., 2^n - 1} appear in U_((2^n)-1)? Next, if g is an element of a finite group G, what can you say about the relationship between o[g] and |G|?
 

1. What is Euler's Totient Function?

Euler's Totient Function, also known as Euler's phi function, is a mathematical function that gives the number of positive integers less than or equal to a given number that are relatively prime to it. In other words, it calculates the number of positive integers that are coprime with the given number.

2. What is the significance of proving the divisibility of phi((2^n)-1) by n?

The proof of this divisibility property is significant because it provides a way to efficiently calculate Euler's Totient Function for very large numbers. This has applications in number theory, cryptography, and computing the order of elements in finite groups.

3. How is Euler's Totient Function related to prime numbers?

Euler's Totient Function is closely related to prime numbers through Euler's theorem, which states that if a and n are coprime positive integers, then a raised to the power of phi(n) is congruent to 1 modulo n. This theorem provides a way to determine if a number is prime by checking its congruence to 1 mod n.

4. What is the general formula for calculating Euler's Totient Function?

The general formula for calculating Euler's Totient Function is phi(n) = n * (1-1/p1) * (1-1/p2) * ... * (1-1/pr), where p1, p2, ..., pr are the distinct prime factors of n. This formula can be used to calculate phi(n) for any positive integer n.

5. How can the divisibility of phi((2^n)-1) by n be proved?

The divisibility of phi((2^n)-1) by n can be proved using mathematical induction and Euler's formula for the totient function. The proof involves showing that if the property holds for a given value of n, it also holds for the next value of n, thus proving it for all positive integers. Detailed proofs and explanations of this property can be found in various mathematical textbooks and online resources.

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