E.164

E.164 is a recommendation by the International Telecommunication Union (ITU) that assigns each country a numerical code (country code) used for international telephone calls.

E.164 is the name of the document that specifies the format, structure, and administrative hierarchy of telephone numbers. The ITU grants country codes to sovereign nations and the administration of the telephone numbers of each country is carried out by the regulator of the corresponding country. An E.164 number is made up of the country code, area or city code, and a telephone number. However, in some countries, dialing within an area or city can be abbreviated, without having to dial the area or city code.