Miscellany

#include <stdio.h>
#include <stdint.h>

int main() {
    uint64_t v = 1234546722732738273LL;
    printf("%02x%02x%02x%02x\n",
            v >> 48,
            v >> 32 & 0xFF,
            v >> 16 & 0xFF,
            v & 0xFF
    );
}