use strict;
use warnings;
use Data::Dump;
use Math::BigInt;

my  $string = '1677259342285725925376';
my  $n      =  Math::BigInt->new($string);
my  @bytes  =  map { ord } split //, $n->to_bytes();
    @bytes  =  map { $_ >= 128 ? $_ - 256 : $_ } @bytes;
dd \@bytes;