. As organizations moved to the cloud (Office 365), Microsoft continued to release "Perpetual" versions for businesses that wanted to buy software once and keep it forever. The "C2R" Shift in your string likely refers to Click-to-Run
If you are looking for a legitimate copy of Office 2016: office201624c2riso160 1732820162x64rp
: Indicates this is the 64-bit version, which is recommended for users working with large data sets in Excel or complex documents. office201624c2riso160 1732820162x64rp