Most iOS and Android devices natively support MP4 playback through their default gallery apps. Troubleshooting Tips If your 5394.mp4 file won't open, consider these steps: Forensic Analysis of Video File Formats - DFRWS
The "5394" is typically a sequential number assigned by a camera’s firmware. For example, some dash cams or action cameras name files sequentially (e.g., 5392.mp4, 5393.mp4, 5394.mp4). Common Origins 5394mp4
Simply right-click the file and select "Open with" to use Windows Media Player . Most iOS and Android devices natively support MP4