We did not make mathematics up.
It's something we observe. A natural language.
1+1=2
e^2=m^2c^4+p^2c^2
The square of the hypotenuses of a right angle triangle is equal to the sum of the square of the remaining two sides.
These are all testable, confirm-able.
That said, the idea of a God could probably play into that fairly well. Some may say that the idea of 'numbers' must have a 'first' instance, something to compare them with. Some may call that God.
It really depends on how 'real' you think a number is.
What is a "number". A place holder? Thinking of singular things...a single apple comes from a tree that produces multiple apples. When was the first apple? Or are we at a snapshot in time in a species drift?
Perhaps there is no "apple", there is only the ever-branching expressions of fruiting bodies.
I suppose one could count the tree as singular, but it depends on the earth and the sun, not to mention countless other microbiota in the soils.
Is the earth a "one"? Well yes and no, the life support function of our planet is mostly driven by it's parent star although there has been a bounty of life found on the floor of the ocean where the only energy source is geothermal vents.
Is our solar system "one"? Kinda. Who knows if the sun would be stable enough on it's own to support life without being a part of the gravitational and electromagnetic dance of the entire galaxy.
Individual galaxies dance around nodes to become parts of super clusters, filaments and sheet walls. Everything upwards in scale from then on is a cloudy, spongy mass of condensing matter within expanding space... We are at the upper limits of material science, and the universe keeps on going.
"It takes the creation of an entire universe to bake a single apple pie." Carl Sagan.
It seems that the existence of any one manifest thing is dependent on the Entirety.