If you’re looking looking for the IMEI (International Mobile Equipment Indicator) or ESN (Electronic Serial Number) number on your cell phone, you don’t need to look far. Depending on your device, your IMEI or ESN number can be found in up to three different places.
Below the battery: If you remove the battery on most devices, you will find a sticker or placard noting the IMEI, ESN, and/or serial number (often abbreviated as S/N).
On the outside of the box: If you have the box your device came in handy, there should be a sticker with a set of numbers and bar codes somewhere on the outside of the box. You should be able to find any information you are looking for here.
Using the handset: On some devices, you may be able to look up the IMEI or ESN number directly on the handset. Of course, this process will vary depending on the manufacturer and model of your device. On a BlackBerry, for example, the ESN and PIN (Personal Identification Number) can be found by opening the ‘Options’ menu and selecting ‘Status.’