528491 - is a prime number.
528491 - on a keypad is [JKL] [ABC] [TUV] [GHI] [WXYZ] [1] - possible combinations are LATIX-1, LATIZone, JAVIZone (Javision?) ... .
528491 - in roman numerals - DXXVMMMCDXCI
528491 - is over 146 hours. 146:48:11 seconds. Or 6 days, 2 hours, 48 minutes, & 11 seconds.
528491 - in days, equates to over 1,447 years.
528491 - transposed into 528 & 491 (reading into the fact that room 528 is directly above room 491 in the movie) 528 / 491 = 1.07535641... 528 - 491 = 37. (528168 would be more interesting in this regard, as 528 / 168 is equivalent to 22/7 ths, a close equivalent of 'pi', signifying the 'circular' motion of perception and creation as Cobb explained.)
528491 - backwards, as a date - 1948, February 5th - a rather unremarkable date in history.
528491 - in hexadecimal pairs = 34 54 5B
528491 - added in a row = 29
52°8' N 49°1' W is a point in the Atlantic ocean northeast of Nove Scotia (Terre Neuve), Canada.
52°8' S 49°1' E is point in the Indian ocean far south of eastern South Africa, close to nothing.
52°8' N 49°1' E is, basically, a small village/town in Russia -named "Olgino" Ольгино.
52°8' S 49°1' W is a point in the southern Atlantic ocean. Roughly 500 miles east of the Falkland Islands.
Takes about 48,600 gallons of jet fuel to fly from Sydney to LAX... that's roughly 184,000 liters.
528491 - quite possibly someone's pin number to her/his debit/credit card. The question then becomes, "who's?" and how much can we withdraw before we're sent to prison?
Based on a lot of supplemental sources I've seen, I'm going to say if 528491 DID actually refer to something significant, C. Nolan probably would have given other clues to allude to a concrete fact / notion.
3502 on a train, '528' & '491' as vertically adjacent room numbers, 528-491 as a partial phone number, ... the only conclusion I can draw is Nolan showing / interpreting how the mind regenerates portions of facts from memory---and, yet incomplete / imperfect memory. I would say that the phone number on the napkin is/was too obvious for movie viewers to recognize .. Nolan put that in there for the audience to pick up on it and for a means to have the team reinforce that number in Robert Fischer's mind as he continues his journey. Interesting that Fischer did not draw the correlation between the napkin phone # and the number he was trying to remember in the bathroom only a few moments later; but, hey, he was under stress, right?
Also interesting to ponder: note that Ariadne (who designed the levels) somehow either had pre-knowledge of what Robert Fischer was going to announce as a number a layer above and made the numbering change on the fly -- working with what they found out as they went -- OR had to advertise / broadcast that number into Robert Fischer's mind prior to entering the first layer of the dream. I can only presume that was part of the van discussion after Robert was put to sleep before the rest of the team followed him down.
D-om
R-obert
E-ames
A-riadne (or A-rthur)
M- ... (gotta be Mal, right? She's the only one with an M-name consistantly in the dreams. Miles & Maurice are both supposedly in reality. I guess Maurice makes a cameo in the hospital room dream...)
S-aito (we never know Mr. Saito's first name)
Odd-balls: Y-usuf, P-hilippa, J-ames, B-rowning, .. not really part of the dream-team, right?
Still, I can't correlate any of that to 528491. VH-7JL either.