E.164 number

E.164 number is an international numbering plan for public telephone systems in which each assigned number contains a country code (CC), a national destination code (NDC), and a subscriber number (SN). There can be up to 15 digits in an E.164 number. The E.164 plan was originally developed by the International Telecommunication Union (ITU).

NENA-STA-010, NENA i3 Standard for Next Generation 9-1-1