HT4061: iOS: How to find the serial number, IMEI, MEID, CDN, and ICCID numberLearn about iOS: How to find the serial number, IMEI, MEID, CDN, and ICCID number
196 Views 3 Replies Latest reply: Jan 24, 2013 7:31 AM by Malignance
Error 21 indicates security software interference > http://support.apple.com/kb/TS3694
It also could, in rare cases, indicate a hardware issue. If you have a hardware issue the warranty only applies in the country you purchased the device.