Find the secret key for this function

[DARKER]

0x90de757572b51cd3 = 10438910133587483859

10419912285387762041 = 521 ^7
10438910133587483859 = ~521,136 ^7 <- this is your number
10560719825892021888 = 522 ^7

but your key is uint64, so this is not possible because ~521,136 is not integer

PS: Other solution can be some another integer, it's case when you strip result to uint64 (last bytes of result are 0x90de757572b51cd3 - it's just end of some big number)