It is a specific bitrate/resolution identifier (1280x720 at 2961k) used by streaming services like CBC Gem .
If so, please provide more context about where you saw the name so I can find the specific "write-up" you need. [gem.cbc.ca] Some episodes have broken audio formats #11547
In various web directories and IPTV (Internet Protocol Television) lists, 2961.mp4 serves as a numerical index for specific movies:
Stored under the identifier turner_video_2961 on the Internet Archive , specifically as a trailer or preview file. 3. Retail & Social Media