Do not use this calculator.
15792089237316195423570985008687907852837564279074904382605163141518161494336/137=115270724359972229369131277435678159509763242912955506442373453587  (DEX)
And now check the calculation with the program.
fffffffffffffffffffffffffffffffebaaedce6af48a03bbfd25e8cd0364140:89=8e03bcbadc7f10d148e03bcbadc7f10c6016427c3bdd8b5755db7996fdc82433  ( HEX)