Calculating Euler phi function

AI Thread Summary
To compute the Euler phi function for a large integer, knowing its prime factorization is essential. For a product of two primes, N = p * q, the function can be calculated using the formula phi(N) = (p-1)(q-1). Implementing this in Matlab requires understanding how to factor N into its prime components. The discussion highlights the challenge of prime factorization, especially for large numbers, which is a key aspect in RSA encryption. Overall, the calculation simplifies significantly when the prime factors are known.
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How do i comput the euler phi function of a large interger?
i know that if p is prime then phi(p)=p-1 and I've found a formula for computing non primes but i don't know how to implement in something like Matlab.
Does anyone know how?
 
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AFAIK, computing the Euler phi function requires you to know the prime factorization of the input. Unless you can find it, there's not much you can do.
 
Yes i know the factorisation problem is hard. I am workin with RSA encryption so we know two large primes, the product of which is N this is what i want to do euler phi on.
Since N is the product of two primes (p and q) is phi(N) simply (p-1)(q-1)?
 

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Seemingly by some mathematical coincidence, a hexagon of sides 2,2,7,7, 11, and 11 can be inscribed in a circle of radius 7. The other day I saw a math problem on line, which they said came from a Polish Olympiad, where you compute the length x of the 3rd side which is the same as the radius, so that the sides of length 2,x, and 11 are inscribed on the arc of a semi-circle. The law of cosines applied twice gives the answer for x of exactly 7, but the arithmetic is so complex that the...
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