Robin's criterion states that the Riemann Hypothesis (RH) is true if and only if Robin's inequality $\sigma(n):=\sum_{ p|n}p<e^{ \gamma} n \log \log n$ is satisfied for $n > 5040$, where $\gamma$ denotes the Euler-Mascheroni constant. We show that if the 2-adic order of n is big enough in comparison to the odd part of n then Robin's inequality is satisfied. We also show that if an positive integer $n$ satisfies either $\nu_2(n) \leq 19$, $\nu_3(n) \leq 12$,$\nu_5(n) \leq 7$, $\nu_7(n) \leq 6$, $\nu_{ 11}(n) \leq 5$ then Robin's inequality is satisfied, where $\nu_p(n)$ is the p-adic order of $n$. In the end we show that $\sigma(n)/n < 1.0000005645 e^{ \gamma}\log \log n$ holds unconditionally for $n > 5040$.
Categories: math.NT