Fischer is forced to come up with a random number while being "held" in a taxi; he says 528491 .
While "52842" is primarily a cinematic Easter egg, the sequence appears in various technical databases and archives:
If you are looking for a specific named "52842.rar," it is likely a fan-made collection of Inception assets (scripts, soundtracks, or wallpapers) or a password-protected file where "52842" is the intended key. EMDB < EMD-52842 - EMBL-EBI
A Local Coverage Determination (LCD) document regarding reconsideration processes.