If you have 7-Zip installed, run 7z l 3187800576.7z in your terminal to list all contained files, their sizes, and original timestamps.
Large game updates or software patches sometimes use internal ID numbers as filenames. 3187800576.7z
Automated backup utilities frequently generate archives named by timestamps or unique database IDs. If you have 7-Zip installed, run 7z l 3187800576
Files with purely numerical names like this often appear in: If you have 7-Zip installed