These are the correct version that you can add in your build.gradle according to the API needs.
API 21:
compile 'com.android.support:appcompat-v7:21.0.1'
compile 'com.android.support:recyclerview-v7:21.0.1'
OR
compile 'com.android.support:appcompat-v7:21.0.2'
compile 'com.android.support:recyclerview-v7:21.0.2'
OR
compile 'com.android.support:appcompat-v7:21.0.3'
compile 'com.android.support:recyclerview-v7:21.0.3'
API 22:
compile 'com.android.support:appcompat-v7:22.0.0'
compile 'com.android.support:recyclerview-v7:22.0.0'
API 23:
compile 'com.android.support:appcompat-v7:23.2.0'
compile 'com.android.support:recyclerview-v7:23.2.0'