If you want to deepen the study of mathematics, you can choose mathematics and applied mathematics. The employment prospects of undergraduates majoring in this major are bleak, and the main way out is to study for graduate students at home or abroad. Suitable for people who can study quietly, but it will be very hard and lonely.
If you don't want to make a breakthrough in theoretical research, there are the following majors to choose from.
1, engineering major, mainly the application of mathematical physics principles, many of which will do research, because all meaningful mathematical physics problems are found in engineering practice. For example, at present, no one in the world can describe the equation of state of fluid in turbulent state, and as long as this equation can be solved and recognized by all people in the industry, it is bound to win the Nobel Prize in physics. (If the Nobel Prize in Mathematics is awarded, it is estimated that you can get a double promise. It's a pity that Nobel doesn't have a math prize. )
If you don't know your future, I suggest you choose such a major. If you come out of this major, you can work, and if you are willing to study, you can continue to study. The way out is wider. However, the study of pure mathematics or physical theory is not so in-depth.
2. Finance major. The mathematics applied by graduate students and doctoral students majoring in finance is not simpler than the mathematics department.