Mail clients or security gateways sometimes rename attachments with a numeric string if the original name is obscured or needs to be unique.
Could you provide on where you found this file or what you believe it contains? Knowing the website of origin or the file's size would help in identifying it. rar file problem.! - Adobe Community 23816.rar
Since the origin of "23816.rar" is ambiguous, follow these security best practices if you have encountered this file: extract them within a secure
If you must investigate the contents, extract them within a secure, isolated virtual machine (sandbox) to prevent potential execution of malicious scripts. 23816.rar