Robin’s criterion states that the Riemann hypothesis is true if and only inequality $$\sigma (n) < e^{\gamma } \times n \log n$$ holds for all natural numbers $$n > 5040$$ , where (n)$$ sum-of-divisors function of $$\gamma \approx 0.57721$$ Euler–Mascheroni constant. We show Robin are not divisible by some prime between 2 1771559. prove when $$\frac{\pi ^{2}}{6} n' \le $$n>5040$$ $$n'$$ square ...