For every pair of positive integers with , denote as the number of positive integers in the range that are coprime with . Find all positive integers such that satisfies these conditions
i) for all .
ii) is divisible by .
For every pair of positive integers with , denote as the number of positive integers in the range that are coprime with . Find all positive integers such that satisfies these conditions
i) for all .
ii) is divisible by .
Firstly, we prove that if satisfies the first condition, then has only one prime divisor. Assume that has at least 2 prime divisors, let be the smallest prime divisor of and be the remaining prime divisors of . We have
Hence, by choosing in i), one can get
which is a contradiction. Therefore, must be a power of a prime. Let , note that
thus and .
If , using LTE, we have
From this, we conclude that and . Similarly, for , applying LTE, we also have
so and .
Therefore, are all desired numbers.