An IMEI (International Mobile Equipment Identity) number is a unique 15-digit serial number that identifies a mobile device on a mobile network. It is usually found printed inside the battery compartment of a phone or on the original packaging. The IMEI number reveals details about a phone, including the brand, model, year of release, and other specifications. It is used by carriers and manufacturers to identify a device on a mobile network and to enable tracking of smartphones that may be stolen or compromised. The number is also used to maintain a blacklist of stolen mobile phones. The IMEI number is different from a serial number, which is used internally by manufacturers.

Knowing the IMEI number of a phone can be useful in several ways. For instance, it can help track down and secure lost or stolen phones. If a phone is stolen, the owner can report the theft to their mobile operator and give them the IMEI number. The operator can then block the phone, preventing the criminal from using it, even if they put in a new SIM card. The IMEI number can also be used by insurance companies or new phone providers to create an insurance policy, and by mobile operators to unlock a device from a previous provider.

To find the IMEI number of a phone, one can dial *#06# on the phones dialer, and the number should appear on the screen. Dual-SIM phones show two IMEI numbers, one for each SIM slot. The number can also be found in the phones settings under "About phone" or on the original packaging. It is a good idea to write down the mobile device’s IMEI number and keep it safe in case it is needed later.