An easy way to retrieve your unique phone serial number, otherwise known as your device’s IMEI number is to open the keypad as if you were going to dial someone, and type in *#06#
As you hit that final hash character, a dialog containing your 15-digit IMEI number will pop-up onscreen, and as always, it is a good idea to note this down somewhere in a safe place for future reference.
Nifty.