ICCID, IMSI and sim serial number explained

The mobile telecoms industry is littered with confusing acronyms and that hasn’t improved with the Internet of Things (IoT) and machine-to-machine (m2M) applications. Some of these acronyms, like ICCID, IMSI and IMEI are important to understand; below we set out some of the key ones involving the SIM card and outline what they mean.

What are the ICCID, IMSI and SIM serial numbers?

The ICCID, IMSI and SIM serial numbers are important identifiers for your SIM cards and mobile connections. You may not need to know what they mean in any great detail, but it’s useful to understand what they are and how they are used. 

And if you’re wondering, the SIM is the Subscriber Identity Module.

What does ICCID mean?

ICCID stands for Integrated Circuit Card Identifier. Basically that means it’s the serial number for the smart card (SIM). Mobile and IOT SIM cards are the largest application for smart cards with billions in use worldwide.
hyphabit sim card

What is the ICCID?

The ICCID is the SIM card serial number. It’s a unique 19 or 20 digit number that’s usually printed on the plastic card that holds the SIM.  The long sequence of numbers can be broken up to tell you more about the card.

The first two digits identify the industry sector. For telecommunications, whether it’s a standard mobile SIM or an IoT SIM card,  this code is 89. The next 2 or 3 digits reflect the country of issue, for the UK this number is 44.

The following digits identify the mobile network code, sometimes referred to as the MNC. This is a number between one and four digits in length and it identifies the network that issued your SIM card. 

The rest of the digits on the SIM card are a unique identifier of that particular card. 

These are followed by a checksum digit calculated from the preceding digits, using the Luhn algorithm

Why do I need to know the ICCID?

You often need to know the ICCID when deploying an IoT application because it’s the main identifier for your SIM card. You’ll usually need the ICCID if you use an online portal to manage your SIMs, want to look up their network status or need to raise a query with your connectivity provider.

What is the IMSI?

The IMSI or International Mobile Subscriber Identity is another unique number that identifies your subscription to a particular cellular network. The IMSI is stored on the SIM. When your device communicates with the network, the IMSI identifies whether or not you’re allowed to connect to that network.

What are multi IMSI SIM cards?

When SIM cards were first introduced there was only one IMSI associated with each physical card. Back then it was envisaged that if you were going to another country or using a different phone, you would move your SIM card between devices. Remember back in the early days of cellular,  mobile phones were big and heavy and often installed in your car! 

Today many SIM cards used for IoT applications often hold multiple IMSIs. This means that the device can switch between different network operators without requiring a different SIM card. This is important for IoT applications that move internationally and require local tariffs for their data charges. Also some applications will need to fail over onto a back up connection in case of a network outage.    

Other useful numbers to know


One of the most likely is the MSISDN, which stands for Mobile Station International Subscriber Directory Number. To you and me that’s the telephone number! In the cellular world, when a telephone number is connected to the network (or provisioned) it is associated with an IMSI.


The other important number you may need to know is the IMEI or the International Mobile Equipment Identity. It’s a unique identifier for the mobile device.

How to find these numbers on your IOT module

To get your ICCID number
Use the command AT+CCID
To get your IMSI
Use the command AT+CIMI
To get your IMEI
Use the command AT+CGSN
To get the MSISDN

Use the command AT+CNUM

The command to get your MSISDN only works if it is stored on the SIM which isn’t always the case.

You may not need to know all these different identifiers, but certain ones, such as the ICCID are important. Knowing what the different numbers mean can help to avoid misunderstandings and confusion, when specifying, developing and debugging your application.
Check out how 2G network closure can affect your IoT deployment.