Since there is no public record of this specific filename in search results, "solid content" for this file would typically depend on where you found it. Here are the most likely possibilities for what it contains:
Many apps (like TikTok, Instagram, or Telegram) rename videos using alphanumeric strings when saving them to your device's local cache. f65few919010.mp4
Some DVR/NVR systems export clips using hex-style timestamps or serial IDs similar to this format. How to safely check the content: Since there is no public record of this