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Existence of a composite n with n+1 dividing σ⁺(n)

Ascertain whether there exists any positive composite integer n such that n+1 divides σ⁺(n), where σ⁺(n)=∏_{p\mid n}(σ(p^{v_p(n)})+1), σ(·) is the sum-of-divisors function, and v_p(n) is the highest power of the prime p dividing n.

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Background

The authors prove several negative cases for σ⁺(n), including that n+1 does not divide σ⁺(n) when n=pq or n=p2q for primes p,q, and they establish bounds relating σ⁺(n)/(n+1) to the abundancy index. A computational search up to 105 revealed no composite n with n+1 dividing σ⁺(n), prompting this explicit existence question.

References

Open question 2: Is there any positive composite integer $n$ such that $n+1\mid \sigma+(n)$?

Divisibility and Sequence Properties of $σ^+$ and $\varphi^+$ (2508.11660 - Mandal, 6 Aug 2025) in Section 2, Main Results (Open question 2)