That appears to be about what the ideal gas law predicts if my back of the envelope (literally) math is accurate.
54 atm isn't really that high of a pressure, about 800 psi. Far more than that in most new carbon dioxide cylinders. And 1 mole of gas is quite a bit.
To see if it sounds reasonable, start with your rule of thumb that 1 mole of gas occupies roughly 20 liters of volume at STP, which is ~1 atm and 273 K (O C). Call the temperature a wash just because this is an order of magnitude estimation. If you scrunch 1 mole of gas down to 0.5 L, that's a factor about 40 compression. Your pressure increases 40x, therefore, that's 40 atm. It's going to be a little higher because of the temperature and slightly more than 1 mole, so 54 atm seems plausible.
Of course, this is all assuming the gas is ideal under these conditions.