American Public University?

[berlinerd]

I'm interested in their BS in Mathematics degree. Its curriculum looks legit.

You can do BA in Mathematics at SNHU (https://www.snhu.edu/online-degrees/bach...athematics) which is definitely a bit more persuasive. For literally the same price per credit and SNHU has a bit more of transfer possible. While AMU/APUS allows for 90 transfer, they allow only 60 with ACE and it's a bit difficult to pick up exactly 60/90. At SNHU it is possible.

I personally think that AMU makes sense if one wants to get cool degrees or certificates like "Counterintelligence", "Homeland Security", etc. Then it looks great. Otherwise there are usually a bit better options for classic degrees.