You can use this website to check the validity of IMEI numbers: http://www.numberingplans.com/?page=analysis&sub=imeinr. This website will also give you other details of your phone if available such as the model number, manufacturer, primary market of your phone, date range of issuance, etc. You can also use the numberingplans.com to check validity of SIM card numbers, phone numbers, IMSI numbers and ISPC numbers.