If you love math that much, get a math degree.
Speaking as an aerospace engineering grad with 35 yrs in the industry, yes, we use a lot of math. No, we don't have time to sit down and do a bunch of 'deriving' solutions. In engineering you generally don't need a mathematically perfect solution anyway, you are just trying to get something close (there will be so many other non-optimum aspects to just about any project that it is kinda pointless to make one tiny portion of the answer come out perfect, and when management gets hold of the whole thing.....) Most of the math I use is already programmed into some 'approved' process or procedure, and I am not supposed to monkey with the guts of the software even if I have an improvement to make (that's a different bunch of guys who take care of that)
I would have to recommend electrical or mechanical engineering. Those degrees will lead to MANY more places to work, places to advance, fields to branch out into.
If you are looking into aero engineering because you think the pay is better, that might be the way it was 30-40-50 years ago but not anymore. These days, management wants to hire 'the best' but only wants to pay average salaries, lays the engineers off whenever it is convenient (for the company), and then thinks they can hire us back any time they want off of any street corner. Add to that, that our congress is trying to balance the budget by chopping defense, that it is darn near impossible these days to find a project (at any company) that is growing, that working on a defense project (which is most of aero engineering) is socially unfashionable these days. Aerospace is about the last engineering recommendation I would make to a kid entering college.
Most of everything we buy already has electronics and computers buried inside it, to help it run optimally and to make the user interfaces (the 'on' button) more usable. Electrical engineering will be more important than ever in our near future, as more products are designed with electrical controls and built-in brains, many even with A.I. to 'know' when you will want to use it and remember your favorite settings, and all the rest.
Mech E is only a half-step behind. Someone has to design all the new products out of new materials using new manufacturing techniques. Even if we outsource the actual production to Antarctica, the company that puts its name on the front of the product will be using engineers to do the design work.
The only time I would recommend aero E to someone is if you just wet yourself over airplanes and missiles, if you just HAVE to be in the middle of this stuff, if you have lived and breathed airplanes since you started walking. You are going to need to have a love of aerospace to be able to last through an entire career of the chicken-stuff and fickle project funding that comes with it.