IMEI stands for The International Mobile Equipment Identity. It is a number unique to every GSM and WCDMA and iDEN mobile phone as well as some satellite phones. It is usually found printed on the phone underneath the battery. All mobile phones are assigned a unique 15 digit IMEI code upon production. You can find it by typing *#06# on your handset.
Now you can check the validity of IMEI number of your mobile phone by visiting NumberingPlans and entering your unique 15 digit IMEI code. After entering 15 digit IMEI code you will get the information regarding manufacturer, model type, and country of approval of a handset.
By the way if you are wondering about the of need of checking the validity of IMEI number of a mobile phone, then here comes the very simple answer:
Suppose your mobile phone with a valid IMEI number is stolen, now if you know your valid IMEI number you can call your network provider and instruct them to “ban” the phone using its IMEI number. Now IMEI number is generally valid when you buy a mobile phone through a cellular operator, but in some other cases there are chances that your newly bought mobile phone may have invalid IMEI number. So its always better to check the validity of your mobile phone’s IMEI number.