For $p$ prime denote by $\mathsf{ord}_p(2)$ the multiplicative order of $2$ modulo $p$. Does there exist $N > 0$ such that, for ALL primes $p$, $\mathsf{ord}_p(2)$ is at least $\frac{(p-1)}{N}$? If there are infinitely many Mersenne primes then the answer is "no". Since the order of $2$ modulo a Mersenne prime $p=2^k-1$ is only $k$, which is not greater than $\frac pN$ for sufficiently large $p$. Is there a proof that the answer is "no"? It is possible that the following question answers this, but it wasn't clear to me: https://mathoverflow.net/questions/123388/the-critical-exponent-in-the-multiplicative-order-of-2-modulo-primes Thanks Steven Galbraith