how many people; a number of people
「何人」 has other readings with different meanings.
パーティーには何人来る予定ですか。
How many people are expected to come to the party?
何人かの同僚がプロジェクトに参加した。
Several colleagues joined the project.
面接に何人の応募者が来るか分からない。
I don't know how many applicants will come for the interview.