IMEI (International Mobile Equipment Identification) is a 15 digit number combination that is unique on your mobile phones. Usually this number is printed inside your mobile phone; you can view it once you remove the battery. Another way to know your IMEI is to key in “*#06#” on your mobile phone and it will give you the 15 digit number. It’s better if you will write it down and keep it so in case you lost your phone you can contact your local operator and you can request to block that handset or mobile phone. Once it is blocked the handset can no longer be used even if they change its SIM.
Note: Blocking the handset thru the IMEI is not always applicable, it still depends on the local operator of your country.