Android: Where does android store system properties key/value

I want to change device's serial number. I have researched and finding some places that android stores prop file: /default.prop /system/build.prop /system/default.prop /vendor/build.prop /data/local.prop /factory/factory.prop On my device, there are just 2 places for storing prop file: /default.prop /system/build.prop But I view those two files and don't see serial number storing here. I also see that serial number is storing at: /data/property/. But as I researched, this directory is just a memory mapping. So I have tried modify and reset device, all values come back to normal value. Please tell me where android store imei/serial number ... Thanks