: Default recording tools on some mobile devices use similar numeric identifiers if a title isn't manually assigned.
The .mp4 extension (MPEG-4 Part 14) is a universal . MP4 files explained: How to open and use - Adobe _-5172676927261.mp4
: These apps often rename media files with numeric strings to keep them unique within their internal databases. : Default recording tools on some mobile devices
The naming convention consisting of an underscore, a long string of numbers (often a timestamp or unique ID), and the .mp4 extension is common to several platforms: _-5172676927261.mp4