God is self-sufficient. Theologians refer to this attribute as "the aseity of God." In his classic book Knowldge of the Holy, A. W. Tozer writes:
Almighty God, just because He is almighty, needs no support. The picture of a nervous, ingratiating God fawning over men to win their favor is not a pleasant one; yet if we look at the popular conception of God, that is precisely what we see.
Twentieth Century Christianity has put God on charity. So lofty is our opinion of ourselves that we find it quite easy, not to say enjoyable, to believe that we are necessary to God. But the truth is that God is not greater for our being, nor would He be less if we did not exist. That we do exist is altogether of God's free determination, not by our desert nor by divine necessity.
For further reflection, see John Piper's article "I Believe in God's Self-Sufficiency."