Android game too heavy after installation!

Hello, I have a really simple android game. Not more than 10 textures and 3 sounds, and all of them really small. (not even 5mb of assets)

But I also have google play services and facebook sdk.

The game APK is 20mb, but after installation it's turning to 50-60MB!!

Why it is so heavy?

I've checked the editor log.

Complete size 6.7 mb 100.0%

I think maybe it's possible to remove some elements from Google play services or Facebook, not sure if this is it that is making it so heavy. On facebook I'm just using Login and share. And on Google play services just the Achievements and LEaderboards.

Thanks.