Translation:What is the phone number of the hospital?
What is the hospital's phone number should be correct. It's a translation and a good one
"What is the phone number for the hospital" is also a perfectly correct English meaning.
[06/02/19] I read somewhere that when you ask the phone number 多少 should be used.
Is it necessary to be accurate? I just forgot the word 'the' and its wrong.
What is the number of a [rather than the] hospital should have been accepted... There are no articles in Chinese??!!