Answer :
The mathematical description that fits to find the circumference of a circle (Approximation we will make to the earth considering it Uniform) is,
[tex]\phi = 2\pi r[/tex]
Here,
r = Radius
The radius of the earth is 6378.01 km or 6378010m
Replacing we have that the circumference of the Earth is
[tex]\phi = 2\pi (6378010m)[/tex]
[tex]\phi = 40074000 m[/tex]
[tex]\phi = 40074*10^3 m[/tex]
Therefore the circumference of the Earth in m with 5 significant figures is [tex]40074*10^3 m[/tex] and using only trailing zeros the answer will be [tex]40074000m[/tex]