‘Number’ is a way of detecting differences within and between states of the universe. The universe is not ‘necessary’. God could exist without one. ‘Godness’ is undifferentiable, so without a universe, ‘number’ would have no meaning, and is therefore, not ‘necessary’.
On the other hand, we may assert that God did, in fact, create a universe, and that the creation of such a universe is therefore part of the essence of Godness. If the essence of Godness includes variability, and therefore difference, then number can be considered part of the ‘necessary’ attributes of God, and thus necessary in itself.
I think on the whole I vote for the second one…