This indicates that the file is the first segment of a "split archive." Large files are often broken into smaller pieces to bypass file size limits on web servers or to make downloading more manageable.
Every subsequent file in the sequence (e.g., .part2.rar , .part3.rar ) must be present in the same folder. 1.6.1.10826.X64.part1.rar
This specific versioning and naming style is frequently seen in: This indicates that the file is the first