g @ m/r**2
where "@" is the symbol which translates as "is proportional to". To use the "=" sign you would have to provide a constant of proportionality which corrects for the type units you are using (English vs Metric, etc).
So the gravitational acceleration (in terms of earth g) at the surface is proportional to the mass and inversely proportional to the square of the radius.
g(planet) = 2.57 / (1.41 x 1.41) = 1.29g(earth)
Not bad, a 100 kilo dude would weigh 129 kilos. We could live there.