Find IMEI Number of Your Lost Phone

IMEI number, a universally unique number associated with your mobile number, uniquely identifies your device within the mobile network. 

If your phone is stolen or gets lost, you would need to provide the IMEI number to the telecom operator for them to blacklist your device and prevent anyone else from using your phone.

If your phone is with you then just by opening phone dialer and dialing *#06#, you can know the IMEI number of your phone. 

But if the phone is stolen and you didn't record your IMEI number then you can retrieve the IMEI number from your Google account.

Just go to google.com/settings and sign-in using your Google account that you had used.

Now click on the android tab, here you'll see all the android devices that are connected to your Google account and it will also show the IMEI number of your phone as well.