[bhritchie]

Philosophers tend to be interested in the "foundational" questions about math and other sciences. In the case of math, in practice this means that good philosophy departments will often teach courses on first order logic and set theory, and philosophers such as Frege and Russell made major contributions in these areas. But they may also get more interested than mathematicians would in the questions about about the nature of logic - the nature of truth, propositions, the viability of alternative or non-classical logics, and so on. And then for example various modal logics can be helpful for thinking about possibility, epistemology, ethics, and so on.

Historically there is also a lot of overlap as well. Formal logic was invented by Aristotle. Leibniz and Descartes are equally large figures in mathematics and in philosophy.

[pvitz]

I don't know the English translations, but Frege's "Die Grundlagen der Arithmetik" are a fascinating piece if one would like to know how modern philosophy of mathematics started and which questions one might ask about mathematics from a philosophical point of view. (https://en.m.wikipedia.org/wiki/The_Foundations_of_Arithmeti...)