I have an iPhone. Does your stuff get automatically transferred to iCloud? And do you need your number to log in or just email?

I have an iPhone. Does your stuff get automatically transferred to iCloud? And do you need your number to log in or just email? - 1

YOU decide what gets saved in the Cloud. And using iTunes, you should also periodically back up your phone to a computer. You need your Apple ID to log in.

By default, if you've set up the phone with an Apple ID, it will automatically be backed up to iCloud periodically. Your Apple ID and password are all you need to log into iCliud by default