You can use IMEI number to check additional information about your device, or if your phone was stolen you can black list your IMEI number and lock it out of the network. Having your phone IMEI number can be usefull, and its very easy to find.
Below you can find a few methods of finding IMEI number.
Using the Dial Pad Dial *#06# in your phone app. Immediately after you do that all of your phone IMEI numbers will be displayed.
In the phone menu Go to phone Settings and then System -> About phone -> Status -> IMEI information.
On the box The IMEI number of ASUS phones is also on the label affixed to the phone box
If you have trouble finding IMEI number of your phone, below you can find a video showing the process on the example of ASUS Zenfone Max