Radius of the Earth is 6400km and that of Mars is 4300000m. Whose radius is bigger and by how much?

Earth’s radius (6400Km, i.e., 6, 400, 000m) is greater than that of earth, by 6, 400, 000 - 4, 300, 000

= 2, 100, 000m

= 2100Km.

(Using the fact that, 1Km = 1000m).