The number of people you’ll need to interview a candidate depends on the role. For example, a higher level role may require more rounds of interviews and more people from different teams to interview the candidate. An entry-level role, on the other hand, may only require one round of interviews with one or two people.
Whatever you decide, involve only as many people as you need. Requiring a candidate to go through multiple rounds of interviews with dozens of people can turn them off and lead to a bad candidate experience. Instead, aim for interviews to include no more than 3-5 people, depending on the role. This may include the  recruiter, the manager, the manager’s manager and/or a peer.