Just a guess, but those numbers look more interesting in hex:
672274793 = 0x28121969
85072278 = 0x05121996
369367448 = 0x16041998
537993216 = 0x20112000
Developers’ or developers’ children’s birthdays?
Regarding finding the syscall implementation, I did a git grep -n LINUX_REBOOT_MAGIC2 and found the definition in kernel/sys.c. The symbol sys_reboot is generated by the SYSCALL_DEFINE4(reboot, ... gubbins, I suspect.