Key numbers for the Rio 2016 Olympic Games which kick open on Friday.

3.5 billion - Each of the previous two Olympic Games drew a global audience of more than 3.5 billion people, roughly half of the Earth's population.

10,500 - More than 10,500 athletes have participated in each of the previous four Olympic Games. The same is expected for Rio 2016.

1000 - United States (977) needs 23 more medals to become the first NOC to win 1000 gold medals at the Olympic Games.

306 - A record total of 306 medal events will be contested at the Rio 2016 Olympic Games.

204 - A total of 204 Olympic Committees were represented at each of the previous two Olympic Games.

47 - Athletics is the sport with most medal events scheduled in Rio. There will be 47 gold medals at stake in athletics events in Rio.

28 - The Rio 2016 Olympic Games are the 28th Olympic Games and Games of the 31st Olympiad, with three previous Games having been cancelled.

27 - Greece, Britain and France are the only NOCs to have won medals at all previous 27 Games. Britain is the only NOC to have won a gold medal in all these Games.

18 - Michael Phelps of the United States holds the record for the most gold medals (18) and the most medals in total (22) at the Olympic Games.

2 - Sports that were not contested at the London 2012 Olympic Games have made it on to the Rio programme. They are golf and rugby sevens.

1 - For the first time in history, the Olympic Games will be staged in South America.