sub hexFromI53{
    my $n = shift;
    my $lo = $n % ( 2**32 );
    my $hi = int( $n / 2**32 );
    return sprintf "%x%08x", $hi, $lo;
};;

print hexFromI53( 24600988483 );;
5ba554b43

print hexFromI53( 9_007_199_254_740_992 );;
20000000000000