print unpack 'H*', pack 'Q>', 654848;;
000000000009fe00

## With a Perl that doesn't support 64-bit ints (Q). 
## Corrected  &.v.% per ikegami++
print unpack 'H*', pack 'NN', int( $n / 2**32 ), $n % 0xffffffff;; 
000000000009fe00