How to reduce apk size in unity 5?

I am trying to build a basic 2d game using simple gui elements. But the lowest apk size is 17.5 mb. Is there any way to reduce this size?
Thanks in advance.

Did you find out.- 1.

With No Extra Material, You can go for only these

  • Use 1 Graphics API
  • Use 1 Architecture if aiming for mobile

else

  • Mesh Quality Compression
  • Texture Quality Compression
  • Sound Quality Compression