LOS ANGELES, Oct 23 (Reuters) - An estimated 21.4 million people watched President Donald Trump debate Democratic challanger Joe Biden on three U.S. broadcast television networks on Thursday, Hollywood publication Variety reported, citing preliminary ratings data.

The figures fell behind initial figures for the pair's first faceoff in September. Updated numbers will be released later on Friday.

(Reporting by Lisa Richwine Editing by Chizu Nomiyama)