Likely a version number, volume indicator, or a tracker ID used to differentiate this specific pack from others in a series (e.g., Pack 140, Pack 141).
Some RAR files are password-protected to prevent antivirus software from scanning the contents while the file is still compressed. The malware only becomes active once you extract it. -packs.xxx 141.rar
This is often used as a descriptive tag for adult-oriented content. It is not a standard functional file extension like .pdf or .jpg , but rather a part of the filename itself to categorize the content for search engines and users. Likely a version number, volume indicator, or a