Find the acceleration due to gravity of Mars

Find the acceleration due to gravity of Mars. Mars has a mass of 6.42 x 10^23 kg and has a radius of 3.40 x 10^3 km.
I am getting a wrong answer g = 3.70427x10^6

You have not changed the units of the radius into m.

g = GM/r²
G =6.67e-11 Nm²/kg²
M= 6.42 x 10^23 kg
r = 3.4 x 10^6 m

g = 6.67e-11*6.42e23/ (3.4e6)² = g = 3.7 m/s²

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Radius should be in metres..... 3.4 x 10^5 m.