A very small file (under 1MB) is likely a short meme or a GIF-style loop.
If you are looking for a review because you found this file on your device or were sent it anonymously: 5125212941360038568.mp4
Because this is a generic system-generated filename, there is no single "official" video or review attached to it. However, Why this filename exists A very small file (under 1MB) is likely
You can upload the file to an online metadata tool to see the "Media Created" date or the original software used to encode it, which can give a clue to its origin. In some internet subcultures, specifically named MP4 strings
In some internet subcultures, specifically named MP4 strings occasionally go viral as "screamers" (jump scares) or "shock videos." If you don't recognize the sender, it is best to avoid opening it. How to identify the content
If you have the file and want to know what it is without playing it:
Files with long numeric strings are frequently used to share memes, but they are also a common format for malware or phishing links.