dbo.SORT temporary run storage: 148643705716736' What does this number means? I totally understand what this error means and how to resolve.
My question is what does this number (148643705716736) referring to?

Date      5/7/2018 1:36:58 AM
Log        SQL Server (Current - 5/7/2018 2:31:00
AM)
Source        spid125
Message
Could not allocate space for object 'dbo.SORT temporary run
storage:  148643705716736' in database 'tempdb' because the 'PRIMARY'
filegroup is full. Create disk space by deleting unneeded files,
dropping objects in the filegroup, adding additional files to the
filegroup, or setting autogrowth on for existing files in the
filegroup.
That is most likely the allocation_unit_id that was attempting to be allocated when it ran out of space. You can check by running the following query to see if tempdb is currently using similar IDs:

SELECT * FROM tempdb.sys.allocation_units;