There are differences.

First, that math must be internally consistent. I don't think I need to argue to r/atheism about the inconsistencies in most religions! Math requires rigour that simply doesn't exist in religion.

Second, that pure math exists separate from the real world. There are a lot of things in math that would make utterly no sense in real-world applications, like infinite sums that can add up to any number you like just by changing the order you add the numbers, or splitting a perfect sphere into tiny pieces and building two more perfect spheres identical to the first. These make perfect sense in math, but not in reality. Hence when math is applied to reality, it is applied through the lens of science, using only those aspects of math that make sense for the situation. Not directly, verbatim, as religion often is.

One could think about religion in a purely hypothetical environment, and that would be closer to what math does, as long as one could maintain the internal consistency. This would probably contradict the real world at some point or another (unless it was a very light dose of religion, like deism), but from a purely hypothetical standpoint the model itself might remain internally consistent, which would be more like math. But due to the contradictions that would cause, it would not likely have many, if any, applications. (Applying such religion willy-nilly to the real world isn't likely to be much better than how Camping "applied" math to the real world to predict its end.)

All that said, I do think it's arguable that math isn't a science (it's certainly not a natural science). It's always an interesting topic of discussion as to whether it's more of an art or a science. (Some universities give it its own category, separate from both!)