The bright star 55 Cancri is known to host five planets, including a transiting super-Earth. The study presented here yields directly determined values for 55 Cncs stellar astrophysical parameters based on improved interferometry: $R=0.943 pm 0.010 R_{odot}$, $T_{rm EFF} = 5196 pm 24$ K. We use isochrone fitting to determine 55 Cncs age to be 10.2 $pm$ 2.5 Gyr, implying a stellar mass of $0.905 pm 0.015 M_{odot}$. Our analysis of the location and extent of the systems habitable zone (0.67--1.32 AU) shows that planet f, with period $sim$ 260 days and $M sin i = 0.155 M_{Jupiter}$, spends the majority of the duration of its elliptical orbit in the circumstellar habitable zone. Though planet f is too massive to harbor liquid water on any planetary surface, we elaborate on the potential of alternative low-mass objects in planet fs vicinity: a large moon, and a low-mass planet on a dynamically stable orbit within the habitable zone. Finally, our direct value for 55 Cancris stellar radius allows for a model-independent calculation of the physical diameter of the transiting super-Earth 55 Cnc e ($sim 2.05 pm 0.15 R_{earth}$), which, depending on the planetary mass assumed, implies a bulk density of 0.76 $rho_{earth}$ or 1.07 $rho_{earth}$.
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