# MSISDN

MSISDN (/ˈɛm ɛs aɪ ɛs diː ɛn/ MISS-den) is a number uniquely identifying a subscription in a Global System for Mobile communications or a Universal Mobile Telecommunications System mobile network. It is the mapping of the telephone number to the subscriber identity module in a mobile or cellular phone. This abbreviation has several interpretations, the most common one being "Mobile Station International Subscriber Directory Number".
The MSISDN and international mobile subscriber identity (IMSI) are two important numbers used for identifying a mobile subscriber. The IMSI is stored in the SIM (the card inserted into the mobile phone), and uniquely identifies the mobile station, its home wireless network, and the home country of the home wireless network. The MSISDN is used for routing calls to the subscriber. The IMSI is often used as a key in the home location register ("subscriber database") and the MSISDN is the number normally dialed to connect a call to the mobile phone. A SIM has a unique IMSI that does not change, while the MSISDN can change in time, i.e. different MSISDNs can be associated with the SIM.
The MSISDN follows the numbering plan defined in the International Telecommunication Standard Sector recommendation E.164.

## Abbreviation

Depending on source or standardization body, the abbreviation MSISDN can be written out in several different ways. These are today the most widespread and common in use.
| Organization | Meaning | Source |
| 3GPP ITU OMA | Mobile Subscriber ISDN Number | Vocabulary for 3GPP Specifications (new) ITU-T Rec. Q.1741-4 (10/2005) Dictionary for OMA Specifications |
| CSPS ITU GSMA | Mobile Station International ISDN Number(s) | MSISDN Format and Details ITU-T Rec. Q.1741-4 (10/2005) Mobile Terms & Acronyms |
| ITU | Mobile International ISDN Number | Vocabulary of Switching and Signalling Terms |

## MSISDN format

The ITU-T recommendation E.164 limits the maximum length of an MSISDN to 15 digits. 1-3 digits are reserved for country code. Prefixes are not included (e.g., 00 prefixes an international MSISDN when dialing from Sweden). Minimum length of the MSISDN is not specified by ITU-T but is instead specified in the national numbering plans by the telecommunications regulator in each country.
In GSM and its variant DCS 1800, MSISDN is built up as
    MSISDN = CC + NDC + SN
    CC = Country Code
    NDC = National Destination Code, identifies one or part of a PLMN
    SN = Subscriber Number
In the GSM variant PCS 1900, MSISDN is built up as
    MSISDN = CC + NPA + SN
    CC = Country Code
    NPA = Number Planning Area
    SN = Subscriber Number
The country code identifies a country or geographical area, and may be between 1-3 digits. The ITU defines and maintains the list of assigned country codes.

### Example

Example Number: +880 15 00121121 (Teletalk Hotline Number) Has the following subscription number:
MSISDN=8801500121121 MSISDN=CCCXXN$_1$N$_2$N$_3$N$_4$N$_5$N$_6$N$_7$N$_8$
| CC/ISD Code | CCC (Example: 880) | Bangladesh |
| NDC/NPA Code | XX (Example: 15) | As allocated by the Government of Bangladesh: Teletalk: 015 Grameenphone: 017 & 013 Banglalink: 019 & 014 Robi: 018 & 016 |
| SN | N$_1$N$_2$N$_3$N$_4$N$_5$N$_6$N$_7$N$_8$ (example: 00121121) | |
For further information on the MSISDN format, see the ITU-T specification E.164.