0549.7z -

: If the file is actually named something like data.7z.0549 , you cannot open it alone; you must have all parts (0001 through 0549) and open the first one to reconstruct the data. To help you further, could you tell me: What is the file size ? Where did you find/download this file?

Here are the most likely possibilities for what this file contains: 0549.7z

Are there with similar names in the same location? : If the file is actually named something like data