At the risk of pointing out the obvious: (1-2^-24) × 2^128 ≈ 3.40282e+38 is the maximum finite single-precision (32-bit) floating-point value, (1-2^-53) × 2^1024 ≈ 1.79769e+308 is the maximum finite double-precision (64-bit) one, and 2^15 = 32767 and 2^31 = 2147483647 are of course the maximum signed 16-bit and 32-bit integer respectively. Also, 2^25 = 33554428 + 4 = 33554400 + 32, which I don’t see a good reason for.
Don’t know why browsers don’t use actual floating-point infinies (which, yes, obey a + Inf = Inf [edit: Inf not a] and a × Inf = (sgn a) Inf for finite a, which should in fact have been covered in either an assembly course or a numerics course). I’m guessing something on the Web ended up subtracting Inf - Inf = NaN and crapping out.