Double major in math and chemistry?

Math + chemistry is a pretty common double major pair, some schools have it as a specific combined major program through the chemistry program. There are a lot of parts of chemistry that are very math-heavy. This combo prepares students to work in theoretical or physical chemistry (this includes things like computationally simulating how proteins fold, or designing nanostructured materials with unusual optical properties).
The math courses required for most chem degrees are just calc 1-3, linear algebra, and sometimes intro statistics, there’s not that much course overlap, so it could take an extra semester to finish all the course work unless you have transfer or AP credit.
Chem + physics or CS are also pretty common (at least amongst the people I’ve met in chemistry grad school).