Is Prince of Space public domain?

[Iron-Confederate]

Hello everyone! This is my first time coming here and I would like to be part of the Riff Trax community.

Now regarding my question, I heard a lot of talk on the interwebs that the movie, Prince of Space is public domain. Is there confirming information to support this rumor or is it just another myth flouting around, courtesy of possible trolls? I want to make sure just so I wouldn't get in trouble for doing something like making and selling a comic that has Phantom of Krankor conquering Mars.