Population Density

The tiny country of Monaco has the world's highest population density. With an area of 3/4 of a square mile and a total population of 32,000, Monaco has a density of almost 43,000 people per square mile

Mongolia is the world's least densely populated country with only 4.3 people per square mile. Australia is a close second with 6.4 people per square mile.
About 90% of the earth's people live on 10% of the land. Additionally, about 90% of the people live north of the equator.
Population density of the continents:

North America - 32 people per square mile
South America - 73 people per square mile
Europe - 134 people per square mile
Asia - 203 people per square mile
Africa - 65 people per square mile
Australia - 6.4 people per square mile

The population density of the planet (including all land area) is about 105 people per square mile. If Antarctica is eliminated (since it has zero population density), the world population density rises only to 115 people per square mile