An ITU-T (International Telecommunication Union - Telecommunication Standardization Sector) standard that defines global telephone number format. As described by the ITU, the E.164 general format must contain only digits split as follows:
- A leader plus sign (`+`)
- Country code (max 3 digits)
- Subscriber number (max 12 digits)
For example, a US phone number would be rendered like this:
[+][1][1234567890]
The following examples demonstrate the format:
US phone number: +11234567890
UK phone number: +4407123456789
SE phone number: +461234567890
We often refer to a telephone number as a MSISDN – Mobile Station International Subscriber Directory Number – for example, a telephone number using international E.164 format. This term is used in quite a few messaging documents. It is sometimes pronounced as “miz-din.” The term: MDN – or Mobile Directory Number – also refers to a telephone number, using the international E.164 format.
