Because ".mp4" is a standard video file container, it is possible this is a corrupted or randomly named video file. If you can provide more context, such as:

you saw this name (e.g., in a download folder, a specific app, or a link)?

it is supposed to be (e.g., a video from a camera or a download from a website)?

A or randomized filename generated during a download or file conversion process. A specific, obscure filename from a local system.