Here is the official content and guidance for downloading (SQL Server Management Studio).
Version 16.5.3 is a very old build (from around 2016). The current modern version of SSMS is 19.x or 20.x . Microsoft no longer provides direct download links for such old versions on their main website, as they are out of support. ssms 16.5.3 download
This version is obsolete. For production systems, always download the latest SSMS from aka.ms/ssmsfullsetup . Here is the official content and guidance for