TITLE: Property (T) and Number Theory?
QUESTION [5 upvotes]: Pardon the wild question, but

Are there any known connections between Kazhdan's property (T) and number theory, or number theoretic consequences of property (T)?

Edit: To clarify, I'd like to know if there are consequences of property (T) in modern number theory that are significant to number theorists, and in what way are they significant (I'm not a number theorist, and so mostly am looking for enrichment on how thing fit together!)
Thanks, in advance, for any thoughts or references!

REPLY [3 votes]: Property $T$ for a real group implies vanishing of the $1$st Betti number for its arithmetic subgroups.  Do you consider this number theory?  (I do.)