How to check if an APK contains native code?
I think this StackOverflow answer should point you in the right direction:


  All of the native code for an app is stored in the libs/ directory in the root of the apk. It's compiled ARM or x86 code, or both. You can find it in libs/architecture_type/lib_name.so. You can dissemble the code with objdump or gdb. Decompiling is a much harder task, but you can find some software that might work for you.