Actually, rotational speed around the Earth is also dependent on altitude above sea level, and a person at the top of a mountain on the Equator is actually travelling faster than 1,660 kilometres per hour (as he has further to go with each revolution). Taking this to an extreme, an object in geostationary orbit around the Earth at an altitude of about 36,000 kilometres above the ground has to travel at about 11,000 kilometres per hour.