The world of mobile phones is full of codes and acronyms that, at first glance, may seem like gibberish. Surely, while tinkering with your phone or managing a portability agreement, you've come across terms like IMSI, ICCID, IMEI, or MSISDN. Far from being mere technical terms, these numbers play a fundamental role in your daily use of your phone, although you probably don't even realize it.
In this article, we'll delve into the universe of these codes, clearly explaining, with everyday examples, what each one means, why they're so important, what they're used for, and how they relate to each other. So the next time you hear one of these acronyms, you'll have a crystal-clear understanding.
What are IMSI, ICCID, IMEI, and MSISDN?
To understand how a simple call or accessing the Internet from your mobile phone works, it is essential to know the role of these codes. Each one identifies a specific element: the IMSI and the ICCID are linked to the SIM card, the IMEI to the device and the MSISDN to your regular phone number.
Let's detail each one:
- ICCID: It is the code that identifies the physical SIM cardThink of it as the chip's unique serial number, engraved both on the card and stored within it. Its main function is to let the operator know exactly which SIM you're talking about, especially in processes such as porting, duplication, or blocking due to theft.
- IMSI: Corresponds to the International Mobile Subscriber IdentityThis is the number that the operator uses to identify you as the one using the network and allows them to authenticate your access. This information is stored inside the SIM card.
- IMEI: Is the International Mobile Equipment IdentifierIt differentiates your mobile phone from other devices worldwide, and its main function is to make it easy to lock in case of theft or loss.
- MSISDN: Under this complicated name hides your mobile phone number, the same one you give to your contacts.
ICCID: The unique number that identifies your SIM
El ICCID (Integrated Circuit Card Identifier) is that long number you've probably seen printed on your SIM card. This identifier allows you to identify each SIM card in the world, just like your own personal ID. Thanks to it, the operator can manage portability, duplicates, or blocking, and is therefore one of the first pieces of information they'll ask you for during these procedures.
La ICCID structure It is defined internationally and is usually 19 or 20 digits long. It usually begins with 89, which indicates that it belongs to telecommunications, followed by the country code (for example, 34 for Spain), a number to identify the operator, and a group of numbers that make each card unique. The last digit is usually a checksum, following the Luhn algorithm, to avoid typing errors.
Where do you find it? It's printed on the physical card (on the plastic part where the SIM came from), but you can also check it from your phone's settings, usually in the "About Phone" or "Status" section. On some devices or operating systems, it's more hidden, but it's usually available. In the IoT and industrial SIM sectors, it can even be printed on the chip itself, a common occurrence when the plastic is disposed of after installation.
What is the ICCID used for? Its main functions are:
- Registration & ActivationWithout the ICCID, the operator would not be able to correctly associate the line or number with the physical chip.
- Security: Allows you to block network access in case your SIM is lost or stolen.
- Internal management: The operator can identify and audit your SIMs, as well as provide services and activate or deactivate lines based on that ICCID.
- Roaming servicesWhen you travel abroad, the destination network can identify the origin of the SIM card thanks to the ICCID.
ICCID and SIM are not the same thing
La SIM card It is the physical chip itself with which you connect your device to the mobile network, while the ICCID It's simply the number that identifies it. That is, a SIM card is like your concert ticket, and the ICCID is the unique serial number for that ticket.
How is the ICCID number interpreted?
The ICCID follows a standardized format. To break down an example, each part contains a relevant information:
- MM: Always “89”, which indicates that it is a telecommunications card.
- CC: The country code according to international numbering (for example, 34 for Spain).
- II: Identifier of the SIM operator or issuer, usually called MNC in mobile network jargon.
- N…N: Account identifier or unique SIM number.
- C: Check digit, calculated from the remainder according to the Luhn algorithm.
The more SIMs are manufactured, the longer this sequence can be. Every SIM in the world is unique thanks to the ICCID.
IMSI: The international identifier of your mobile line
El IMSI (International Mobile Subscriber Identity) is the number the operator uses to identify, authenticate, and associate a specific mobile line with the user. The curious thing is that, although it's engraved on the SIM card, it's not usually printed on it (unlike the ICCID), so we usually don't see it, even though our phone uses it constantly.
This code generally has 15 digits and is composed of:
- MCC (Country code): Three digits number the country (for example, 214 for Spain, 334 for Mexico).
- MNC (Operator/Network Code): Two to three digits that identify the mobile network or operator.
- MSIN (Mobile Subscriber Identity Number): The rest of the digits, unique for each line.
The IMSI is essential for the functioning of the mobile network, as it indicates which network the user should connect to, allows authentication management, and, during international roaming, informs foreign networks which operator they should "request permission" from to bill and route communications.
Its importance lies in the fact that it is the number by which the operator truly recognizes you, and it is associated with the contracted line, regardless of your telephone number. If you lose the SIM If you request a duplicate IMSI, the IMSI can change, but it generally remains linked to your line until you change carriers. If you change carriers through portability, the IMSI will be new.
IMSI vs ICCID: Key Differences
The key to not getting confused: ICCID identifies the physical SIM (the “plastic”), while IMSI Identify the subscription or mobile line (the service you have contracted with the operator).
- A single SIM can have multiple IMSIs (in Multi-IMSIs, which are often used in IoT or businesses).
- When changing SIMs, the ICCID changes, but you can keep the same IMSI depending on the case.
- The IMSI is private (not printed on the SIM), while the ICCID is visible.
Where is the IMSI? How do I check it?
Most users never see their IMSI. It's stored on the SIM and used internally by the phone for authentication. You can check it through specialized apps, by accessing hidden menus on your phone, or by asking your carrier, but it's not displayed by default, especially on closed systems like the iPhone.
IMEI: The unique identifier of your mobile device
El IMEI (International Mobile Equipment Identity) is a 15-digit number unique to each mobile device, whether it's a smartphone, tablet, or other device with access to a mobile network. It's recorded on the device itself, not on the SIM, so the IMEI remains the same if you change SIMs.
Its main function is to globally identify your device. Operators use it, for example, to block a device in the event of theft, preventing it from working even with another SIM. In corporate management systems, such as IoT, it allows you to apply rules, alarms, and black and white lists, preventing fraud and overbilling. It's also useful for learning what IMSI and ICCID are and better understanding their relationship in the mobile network.
The usual structure is:
- 8 digits that identify the type of device.
- 6 unique digits for each device.
- 1 check digit.
You can check the IMEI on your phone by dialing *#06#, checking the box or receipt, or in your device's settings. It's especially useful to have it handy in case you need to lock your phone after a theft.
MSISDN: Your phone number on the network
The abbreviation MSISDN Mobile Station Integrated Services Digital Network Number (MSDN) is the technical name for your mobile phone number, which you give to your contacts, including the country code and national prefix. Its main feature is that it's not tied to a SIM or carrier, allowing for portability between different carriers without losing your phone number.
Is used for:
- Identify yourself to other users.
- Route calls and messages to your device.
- Link services and accounts to your mobile line.
The MSISDN is not stored on the SIM; rather, the operator maintains a table linking each IMSI (the line) to the MSISDN (the number dialed by others). This allows you to keep the number after porting, allow multiple numbers to be associated with the same SIM, or manage locks and ownership changes without changing the physical line.
How to check these codes on your mobile phone?
If you're curious to find out what these numbers are on your device, here's a handy little guide:
- ICCID: Printed on the SIM card or available in the phone settings (“About phone”, “Status” or similar section).
- IMSI: Difficult to check directly. It may be in advanced settings menus, through third-party apps, or by asking your operator.
- IMEI: By dialing *#06# on the phone, checking the cash register, invoice or settings.
- MSISDN: This is your phone number. It usually appears in messaging apps, phone settings, or hidden menus when you dial codes like *#*#4636#*#*.
What about mobile phone security and fraud?
Knowing and using these codes correctly is key to avoiding security issues, such as the dreaded identity theft or SIM card duplication and portability fraud. For example:
- YES Swap: A criminal obtains a SIM card with your number (MSISDN), but if the operator verifies that the ICCID or IMSI do not match, they can block the theft.
- IMEI lockIf your phone is stolen, the operator can disable it even if they change the SIM, thanks to the IMEI.
- Recycling numbers: Carriers recycle unused MSISDNs, which can pose privacy issues if the old number receives important messages or calls.
- Portability and SIM change: When changing operators, the number (MSISDN) remains the same, but the ICCID and possibly the IMSI change.
That's why it's so important that your online security includes authentication based on both the phone number and the physical SIM, and not just one of them, to reduce the risks of identity theft or fraud.
New scenarios in IoT: Multi-IMSI SIM, eSIM, and connectivity security
With the rise of Internet of Things (IoT), concepts such as cards have emerged Multi-IMSI and eSIM (Virtual SIMs). Multi-IMSIs allow a single SIM to have multiple subscriber identities, hopping between different networks and countries without changing cards. eSIM They store multiple operator profiles and are managed remotely.
In these scenarios, it is essential to correctly identify SIMs and profiles using both the classic ICCID and new identifiers (such as eUICCID or eID in eSIM) to ensure secure, efficient, and globally manageable communication for both individual and business users.
Practical examples of the relationship between IMSI, ICCID, IMEI and MSISDN
To facilitate understanding, let's look at some real cases:
- 1 case: You change your mobile phone, but you keep your SIM. Here, the IMEI changes because it is another device, but the ICCID and the IMSI remain the same, and you MSISDN (phone number) too.
- 2 case: You port to another operator. The new SIM card implies changes in ICCID y IMSI, but you MSISDN It is maintained thanks to the operator's management.
- 3 case: Your mobile phone is stolen and you request a duplicate SIM. ICCID will be new, the IMSI will probably change too, but you MSISDN It remains the same.
Management and international regulation of these codes
The assignment and management of these identifiers is not random. International Telecommunications Union The International Telecommunication Union (ITU) defines standards for ICCID, IMSI, IMEI, and MSISDN, assigning ranges and encoding numbers to ensure global uniqueness. Each country adapts these rules to its needs, and operators rigorously manage this data to prevent duplication, fraud, or security breaches. To learn more, you can also visit .
Although the structures are similar worldwide, the format and specific prefixes may vary by region and operator, ensuring coordinated and secure management internationally.
It's clear that behind the apparent simplicity of dialing a number or using a mobile phone, there's a complex infrastructure that ensures the system functions correctly and securely. IMSI, ICCID, IMEI, and MSISDN codes are the basis for identification, authentication, and protection in mobile telephony, allowing you to communicate, browse, and maintain your digital identity securely in this increasingly connected era. Share the information and more people will know about the topic..
