  By analyzing the $R$ values measured at 68 energy points in the energy region
between 3.650 and 3.872 GeV reported in our previous paper, we have precisely
measured the mass, the total width, the leptonic width and the leptonic decay
branching fraction of the $\psi(3770)$ to be ${M}_{\psi(3770)}=3772.4 \pm 0.4
\pm 0.3$ MeV, $\Gamma_{\psi(3770)}^{\rm tot} = 28.6 \pm 1.2 \pm 0.2$ MeV,
$\Gamma_{\psi(3770)}^{ee} = 279 \pm 11 \pm 13$ eV and $B[\psi(3770)\to
e^+e^-]=(0.98\pm 0.04\pm 0.04)\times 10^{-5}$, respectively, which result in
the observed cross section $\sigma^{\rm obs}[e^+e^-\to \psi(3770)]=7.25\pm 0.27
\pm 0.34$ nb at $\sqrt{s}=3772.4$ MeV. We have also measured $R_{\rm
uds}=2.121\pm 0.023 \pm 0.084$ for the continuum light hadron production in the
region from 3.650 to 3.872 GeV.
