Determine all non-negative integers n smaller than 12897 which have exactly 2019 positive divisors.
Solution
Numbers with exactly 2019 positive divisors are either of the form p2018 or p672⋅q2 for distinct prime numbers p and q. The number 12897 can be written as 12897=(27)97=2679. As p is at least 2, the number p2018 is greater than 2679 and therefore, the case n=p2018 is impossible. Thus we have n=p672⋅q2 with p672⋅q2<2679. Hence p=2 and as q2<27=128, q is one of the primes 3, 5, 7 or 11.
Answer. There are 4 solutions: n=2672⋅32 or n=2672⋅52 or n=2672⋅72 or n=2672⋅112.
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