CRC-64/XZ (ECMA-182): reflected polynomial 0xC96C5795D7870F42, init 0xFFFFFFFFFFFFFFFF, final XOR 0xFFFFFFFFFFFFFFFF. This is the integrity check used by the .xz container (and an optional 7z check).
Check value: CRC64("123456789") == 0x995DC9BBDF1939FA.