Very small files (under 100KB) are often simple documents or scripts. Very large files are likely data backups or software.
If you are confident the file is legitimate, you will need a utility that supports the .7z format: The standard free, open-source tool for these files. WinRAR / Keka: Common alternatives for Windows and Mac. 185872.7z
Before opening the archive, you should scan it using an online multi-engine scanner. This will tell you if any antivirus software recognizes the contents as a threat: Very small files (under 100KB) are often simple
Does the date the file was created or modified align with an action you took online (like requesting a data export)? 4. How to Open it Safely WinRAR / Keka: Common alternatives for Windows and Mac
If you received this as an unsolicited attachment, do not open it . Attackers often use numeric filenames like this to bypass basic spam filters.