E.164 is the International Telecommunication Union's (ITU) standard for international phone numbers. An E.164 formatted phone number is the country code followed by either a global subscriber number or a national destination code and a subscriber number. The overall number is limited to 15 digits, and it is commonly shown with a "+" in front of it. For example, a United States number that may commonly be formatted like "(949) 555-1212" would be "+19495551212" in E.164 format.

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