IMEI(International Mobile Station Equipment Identity) is a 15 digit unique number, using which law enforcement authorities can track your phone with the help of network service providers. If you loose your phone and do not have access to your phone bill or the box, there is still a way to recover the IMEI number.
How to get IMEI number?
If you still have your phone, you can dial *#06# to get the 15 digit number. If you have already lost the phone, you can get it by logging into your google account – which you used in your phone to access Google Play Store. Now go to Google Settings. Click on Expand All or the android icon and you’ll get the IMEI number and other details of your phone.
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What to do with IMEI number?
You can register an FIR(First Information Report) and ask service providers to either track the phone or block it, so that no one else can use their service on your phone.