I signed up before Facebook ever required phone numbers. I never gave Facebook my phone number. I never had a Facebook app on any Android device, ever. When

I signed up before Facebook ever required phone numbers. I never gave Facebook my phone number. I never had a Facebook app on any Android device, ever. When I use Facebook, it's in a sandboxed browser that I never log into any other site with. Facebook, for a time, started autofilling a prompt with my phone number, asking me to complete my account setup. When Facebook has an app and all the people you know send their contacts to it, they don't need you to give them your phone number for them to have it.