If your device doesn't recognize it, you can often simply rename the .m4v to .mp4 without damaging the file.

Open it with VLC Media Player or MPC-HC. These players bypass most container issues and can play the video even if it's just a renamed MP4.

The .m4v extension is a video container format developed by Apple. It is nearly identical to MP4 but may contain DRM copy protection (FairPlay) if it originated from the iTunes Store.

Filenames starting with 1_ followed by a long string of digits are characteristic of files downloaded from Telegram or similar encrypted messaging services that rename files upon upload.

While playing in VLC, go to Tools > Media Information . This may reveal the actual movie title, director, or studio in the "Title" or "Comments" field.