Universal odd-prime valuation bound for the sum of divisors

From papers

Let p>2p>2 be a fixed prime, and let nNn\in\mathbb{N}. Write σ(n)\sigma(n) for the sum of the positive divisors of nn, and let νp\nu_p denote the pp-adic valuation. For a prime qnq\mid n, write νq(n)\nu_q(n) for the exponent of qq in nn. The relevant conditions are: (1) every prime qq dividing nn satisfies νp(σ(qνq(n)))logp(qνq(n))\nu_p(\sigma(q^{\nu_q(n)}))\leq\lfloor\log_p(q^{\nu_q(n)})\rfloor; or (2) every prime qq dividing nn that satisfies νp(σ(qνq(n)))=logp(qνq(n))\nu_p(\sigma(q^{\nu_q(n)}))=\lceil\log_p(q^{\nu_q(n)})\rceil is less than pp.

Universal odd-prime valuation conjecture. Every nNn\in\mathbb{N} satisfies condition (1) or (2). Consequently,

up(σ(n))logpn.u_p(\sigma(n))\leq\lceil\log_p n\rceil.

A complete characterization of the indices nn for which equality holds in this bound remains open, although the bound is proved under the stated conditions.

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Primary source

Tewodros Amdeberhan, Victor H. Moll, Vaishavi Sharma and Diego Villamizar, “Arithmetic properties of the sum of divisors”, arXiv:2007.03088 (2020).

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