Can God serve as a part?

Can God serve as a part of the greater whole? Now, I know that this question may seem really silly, but it's actually really important. After all, what is a part? A part is something inherently deficent and incomplete. If God can be thought of as a part of something greater, then He wouldn't be perfect. And He wouldn't be self-sufficient either, since He would be in need of others to complete Him. It also follows that He wouldn't even exist necessarily, since a part is something that can always be replaced.