I wanted to do math/philosophy, but despite how well ranked our philosophy department is, I felt like I would get more value out of studying economics in addition to math (unfortunately, by the time I made this decision, it was too late to double major, so I'm doing econ as a minor).

I love philosophy to death, and it is actually for this reason that I'm comfortable not majoring in it. You're right that philosophy is really valuable in terms of enhancing your reasoning, writing, reading, and logic skills, but it's something you could engage in as a hobby (especially with the fact that students have access to all sorts of journals, articles, books, etc). So for me at least, studying philosophy as a hobby is exceedingly easy. You can just maintain a blog and engage in philosophy forums for better writing skills.

Do take a few courses, meet professors in the department, and engage in philosophy club, though! My point is just that a philosophy major probably won't add a whole lot of extra value to your education unless you have trouble studying it on your own or want to study philosophy in graduate school (risky choice, but respectable!).

My impression of the economics department, however, is not that great. It's not rigorous enough to be respectable, in my experience. I would say maybe just take a few courses in econ (introductory and intermediate macro and micro, along with econometrics, for example). I think it's useful to have taken at least a few economics courses regardless of major, given just how important the subject is.

Math is an excellent major, but I would not recommend it on its own, unless you know you're going to graduate school for math. Our math department is so amazing, and it's ranked 16th internationally! So many good professors (in my opinion).

Computer science is another excellent major, though you might be able to get away with taking just a few core courses, if your goal is just to land a programming job.

If I could go back in time, I think I would have done math, physics (or alternatively, CS), and some kind of engineering. I know of a couple folks triple majoring in this fashion and I think it is these folks who are getting the most value out of their education. If that's too much, I would say math and physics, math and CS (I know TONS of folks doing this!) or math and some kind of engineering.