What is the circumference of the Earth along the Prime Meridian?

The Prime Meridian only extends from the North Pole to the South Pole along the 0° longitude line,

which is only half of the Earth's circumference.

The circumference of the Earth that includes the Prime Meridian is a polar circumference measuring approximately 40,008 km (about 24,860 miles), which is shorter than the equatorial circumference by about 67 km (42 miles), not including elevation above or below MSL.