The International Telecommunication Union sets a one- to three-digit code for each country, and those codes serve as part of the telephone number for long-distance calls. Examples include 48 for Poland, 677 for the Solomon Islands and 976 for Mongolia.
Some countries share country codes. For instance, Russia and Kazakhstan both share 7 as their country code, while the United States, Canada and many island nations in the Caribbean all use 1 as their code. When dialing countries whose country code is not 1 from the United States, callers should begin with 011 and then the country code. A city code or area code and then a unique phone number for the party being called usually follow immediately after the country code. However, international calls made to mobile phones require an alternate numeric format after the country code, notes the Federal Communications Commission.
While country codes are in place for each country, the entire continent of Antarctica, which contains no countries, has no codes assigned to it, according to the CIA. Calls to Antarctica either use the code for the country associated with the research station being called or a special country-level code assigned by the International Telecommunication Union for calls via Inmarsat, a satellite-based telecommunications service serving remote regions.