A phone number. You mean the thing that you hand out to strangers so that they can contact you? The thing that was designed from the start to be shared, and used to be listed in a big book that everyone had? The thing that you put on top of the paper that you hand out to dozens of companies when looking for a job?

What are you concerned about with your phone number? In what way does Signal (or anyone) having your phone number undermine your security?