List of country calling codes
Country calling codes, country dial-in codes, international subscriber dialing (ISD) codes, or most commonly, telephone country codes are telephone number prefixes for reaching telephone subscribers in foreign countries or areas via international telecommunication networks. Country codes are defined by the International Telecommunication Union (ITU) in ITU-T standards E.123 and E.164. The prefixes enable international direct dialing (IDD).
Country codes constitute the international telephone numbering plan. They are used only when dialing a telephone number in a country or world region other than the caller's. Country codes are dialed before the national telephone number, but require at least one additional prefix, the international call prefix which is an exit code from the national numbering plan to the international one. In most countries, this prefix is 00, an ITU recommendation; it is 011 in the countries of the North American Numbering Plan while a minority of countries use other prefixes.