Unlike standard ZIP files, Windows and macOS usually require third-party software to extract RAR archives:
The official tool created by Eugene Roshal (the "RAR" namesake) for full management of these archives.
A is a proprietary archive format used for high-efficiency data compression. The file "21710.rar" specifically appears to be a compressed "container" that can hold multiple files or folders in a smaller, single-package format. What is in a "21710.rar" File? RAR files are typically used for: