With Australia you usually connect only the largest landmass of the Australian country, but the continent itself consists of several countries. Strictly taken, the Heard and McDonald Islands also belong to the country of Australia but are geographically attributed to the Antarctic continent.
Australia consists of 5 different countries with a total surface of 8.01 million km². This corresponds to a share of 5% of the habitable earth surface. The coastlines in and around Australia altogether have a lentgh of 41,091 km. In these 5 countries are living 27.47 million people (=0.38% of the world's population).