Quite a lot! I work in a university with hundreds (maybe thousands!) of staff, but in my department there are approximately 20 members of academic staff. I probably work closely with about five of them (on research and similar teaching areas).
I work in a research group with 5 other people and one boss. My boss is a lecturer in the school of chemistry. But I pretty much work alone 🙁 I’m the only person that is working on a diagnostic blood test for cancer 🙁
4 Ph.D. students, 1 research assistant, 1 other postdoc, 1 boss, + all the hundreds of people with in my Institute and outside who work on related topics. Scientists build on each others science and expertise so we all work together, even if its informally.