In terms of density, Mongolia is the least populated country in the world. It has population of 2,646,487 in the area of 1,564,116 square kilometers, which makes 1.7 people per square kilometer. On the other hand, Macau has the highest density with 18,534 people per square kilometer.

In terms of number of people, Vatican City is the least populated country with the population of 832 (2011 July estimate). However, the density is 1877 people per square kilometer, which makes Vatican the 6th most populated country.