Question

How may participant can be in one conference call?

Answer 1

As many as you please, depending on the service that you use

Viber allows up to 39 participants in a group call, while on Whatsapp you can only add 30 participants to a similar call

Answer 2

It depends on what kind of conference call software you're using. For me and my colleagues, we all use ezTalks on our computers and smartphones. The free version of ezTalks allows up to 100 participants per meeting.