: You must always open the first file in the sequence (usually the one ending in .rar or .part01.rar ).
: If you get a "Checksum Error," one of the volumes (potentially the .r21 file itself) may have been corrupted during the download and needs to be re-downloaded. R21 File Extension - What is .r21 and how to open? Download r21 rar
Understanding the .R21 File: How to Handle Multi-Volume RAR Archives : You must always open the first file
: Many file-hosting services have a maximum size per upload. Download r21 rar
: The number "21" indicates that this is the 21st part of a compressed archive.
: Downloading multiple smaller files can sometimes be faster or more reliable than one massive download. How to Open and Extract .R21 Files