phonenumber

A phone number is a numeric sequence that uniquely identifies a telephone line within a global telecommunications network. It enables routing of voice calls, SMS messages, and other services to a specific subscriber or service. Numbers may be assigned to individuals, organizations, mobile devices, or virtual services and can be portable across networks in many regions.

Most countries structure numbers according to the ITU-T E.164 international numbering plan. An E.164 number typically comprises a country calling code, a national destination (area) code, and a subscriber number, with a maximum of 15 digits in total. The internationally standardized format uses a leading plus sign and the digits, for example, [phone].

Different types exist, including fixed-line (landline), mobile, toll-free, and VoIP or virtual numbers. National formats vary by country; spacing, parentheses, or dashes are common for readability. In many systems, short codes or shortened numbers are used for services such as emergency or customer support.

Number ownership and management are handled by national regulators and numbering administrations. Regulations typically include number allocation, routing rules, and porting procedures that allow customers to switch providers without changing their number in a process known as number portability. Privacy and security considerations address misuse such as spoofing or harvesting numbers.

For dialing, international calls use an access code or the universal plus prefix followed by the country code and subscriber number. Mobile networks typically support the + prefix directly. Phone numbers are widely used beyond voice, notably for SMS-based verification and two-factor authentication, which makes their accuracy and privacy increasingly important.