Not sure if this has ever been covered before, but apparently the Gold Cap in the game

Is 9,007,199,254,740,991. Or nine quadrillion seven trillion one hundred ninety-nine billion two hundred fifty-four million seven hundred forty thousand nine hundred ninety-one.
Or for the computer geeky, it is 2^53. The largest mantissa in standard IEEE754 double precision fp format. More or less the maximum integer you can represent in 64 bit double precision fp with full precision.