My students learn in the intro to astrophysics class that the characteristic photon diffusion time scales as:

t_diff = <N> * <l> / c
or about 3 (R/<l>)^2 * <l> /c, where <N> is the mean number of interactions per escape, <l> is some usefully typical photon mean free path, c is the speed of light in the vacuum, and R is the star's radius.

This works out to be:

154,000 yrs * (R/R_sun)^2/(<l>/1 mm), where the characteristic photon mean free path is given in units of millimeters (more appropriate than cm in our Sun), essentially what KenG said it was, in the case of our Sun.