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If we letf(n)  denote the sum of all the positive divisors of the integer n, how many intergers i exist such that 1 <= i <=  2010 and  \(f(i) = i + 1\)?

 May 8, 2022
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If f(i) = i + 1, the only divisors of i are 1 and i. That means i is a prime. You can calculate the number of primes in the given range for your answer.

 May 8, 2022

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