It is normally 15 digits long.
Simply press *#06# on your phone’s keypad and a long number will be displayed on the screen of the phone. The IMEI number we require is the first 15 digits of this number (ignore any “/” or “-” characters). Alternatively you will find it on a label on the back of your phone, underneath the battery showing the same number (ignore any “/” or “-” characters). The IMEI number comes in handy if a mobile phone is stolen, as the GSM network can identify the device and stop it from accessing the network.  International Mobile Equipment Identity. To find out your mobile phone's IMEI number, type (see below for exceptions) : * # 0 6 #. into your mobile phone handset. As you complete the above code, your mobile phone's IMEI number will be displayed on the screen. Alternatively, you can also find the IMEI number recorded on an identification sticker, normally located on the rear of the handset and underneath the batter On these devices, you'll find the serial number in the Settings menu and the IMEI/MEID (the MEID is the first 14 digits of the IMEI) on the back. If you need support but you can't get to the Settings menu, you can use the IMEI/MEID instead of the serial number: 1  iPhone 6 Plus. 2  iPhone 6.  1 Most phones will tell you when the number is displayed if it is an IMEI or MEID number. 2  If your phone doesn't you can verify which number it is by checking what carrier you use. 3  GSM networks like AT&T and T-Mobile use IMEI numbers. 4  CDMA networks such as Sprint, Verizon, and US Cellular use MEID numbers. You can retrieve the IMEI/MEID number on virtually any phone by dialing in the universal code. Dial *#06#. You typically will not need to press the Call or Send button, as the IMEI/MEID number will appear as soon as you finish dialing the code. Dial the IMEI code. You can retrieve the IMEI/MEID number on virtually any phone by dialing in the universal code. Dial *#06#. You typically will not need to press the Call or Send button, as the IMEI/MEID number will appear as soon as you finish dialing the code. The IMEI number is used by a GSM network to identify valid devices and therefore can be used for stopping a stolen phone from accessing that network. For example, if a mobile phone is stolen, the owner can call his or her network provider and instruct them to blacklist the phone using its IMEI number. The last number of the IMEI is a check digit calculated using the Luhn algorithm, as defined in the IMEI Allocation and Approval Guidelines : The Check Digit shall be calculated according to Luhn formula (ISO/IEC 7812). (See GSM 02.16 / 3GPP 22.016). The IMEI (International Mobile Equipment Identity) is a unique 15 or 17 digit code used to identify an individual mobile station to a GSM or UMTS network. IMEI numbers either come in a 15 digit or 17 digit sequences of numbers. These numbers can identify a handset. Currently the format of the IMEI is AA-BBBBBB-CCCCCC-D.  1 If the phone has an IMEI number but you are on a network that uses MEID numbers, ignore the last digit (IMEI is 15 digits, MEID is 14 digits). 2  GSM networks like AT&T and T-Mobile use IMEI numbers. 3  CDMA networks such as Sprint, Verizon, and US Cellular use MEID numbers. You can retrieve the IMEI/MEID number on virtually any phone by dialing in the universal code. Dial *#06#. You typically will not need to press the Call or Send button, as the IMEI/MEID number will appear as soon as you finish dialing the code. The IMEI (15 decimal digits: 14 digits plus a check digit) or IMEISV (16 digits) includes information on the origin, model, and serial number of the device. The structure of the IMEI/SV are specified in 3GPP TS 23.003. The last number of the IMEI is a check digit calculated using the Luhn algorithm, as defined in the IMEI Allocation and Approval Guidelines : The Check Digit shall be calculated according to Luhn formula (ISO/IEC 7812). (See GSM 02.16 / 3GPP 22.016). It is normally 15 digits long. The IMEI number can be found on the silver sticker on the back of your phone, under the battery pack, or on the box your phone came in. You can also display the IMEI number on the screen of your mobile phone or smartphone by entering *#06# into the keypad
http://www.mobileinsurance.co.uk/faq/what-is-my-imei-number-and-how-do-i-find-it/ http://www.imei.org.uk/myimei/ https://support.apple.com/en-us/HT204073 http://www.wikihow.com/Find-the-IMEI-or-MEID-Number-on-a-Mobile-Phone http://www.wikihow.com/Find-the-IMEI-or-MEID-Number-on-a-Mobile-Phone https://en.wikipedia.org/wiki/International_Mobile_Equipment_Identity https://in.answers.yahoo.com/question/index?qid=20070821075144AAeQwr6 http://www.wikihow.com/Find-the-IMEI-or-MEID-Number-on-a-Mobile-Phone https://en.wikipedia.org/wiki/International_Mobile_Equipment_Identity http://support.bell.ca/Mobility/Smartphones_and_mobile_internet/What_is_an_IMEI_number_and_how_can_I_find_mine
how long is an imei number