I am interested in obtaining an upper bound for $\prod\_{p|N} (1 + 1/\sqrt{p})$ when $N$ is squarefree. It's not too hard to show that 
$$
\prod\_{p\mid N} (1 + 1/\sqrt{p}) \ll C^{\omega(N)} \ll N^{\varepsilon}
$$
for any $\varepsilon > 0$. I was wondering is it possibly to prove an upper bound $\ll \log N$ or some power of $\log N$? Any comments would be appreciated. Thank you. 



How to obtain an upper bound for $\prod_{p\mid N} (1 + 1/\sqrt{p})$ where $N$ is square free?
The $N$ for which this product is largest will be of the form $N = \prod\_{p<y} p$, so that $\log N \sim y$. For this $N$,
$$
\log \prod\_{p\mid N} \bigg( 1+\frac1{\sqrt p} \bigg) = \sum\_{p\mid N} \log \bigg( 1+\frac1{\sqrt p} \bigg) \sim \sum\_{p\mid N} \frac1{\sqrt p} = \sum\_{p<y} \frac1{\sqrt p} \sim \frac{\sqrt y}{\log y} \sim \frac{\sqrt{\log N}}{\log\log N},
$$
and so
$$
\prod\_{p\mid N} \bigg( 1+\frac1{\sqrt p} \bigg) = \exp\bigg( (1+o(1)) \frac{\sqrt{\log N}}{\log\log N} \bigg)
$$
for these $N$ (and the right-hand side will be an upper bound for all $N$). In particular, an upper bound of $(\log N)^A$ is too ambitious.


Reality check: replacing $1+1/\sqrt p$ by $1+1$ and carrying this computation through will recover the more familiar bound
$$
2^{\omega(N)} \le \exp\bigg( (\log2+o(1)) \frac{\log N}{\log\log N} \bigg).
$$


