It is a RAR (Roshal Archive) file, specifically a "split" or "spanned" volume. This means the original data was too large for a single file and was divided into multiple parts (e.g., part01, part02... part21).
If you must investigate the file, do so in a strictly isolated virtual machine or sandbox environment to prevent potential infection of your host system. Gh0stb.part21.rar
To successfully extract the contents of this file, a user must possess all other parts of the archive. If any part is missing or corrupted, the extraction process will fail. It is a RAR (Roshal Archive) file, specifically