when i use

printf "%064Xn" $((0x1a838b13505b26867))

the number one was truncated

000000000000000000000000000000000000000000000000A838B13505B26867

with big hex/number is worse

printf "%064Xn" $((0x349b84b6431a6c4ef1))
0000000000000000000000000000000000000000000000009B84B6431A6C4EF1

number has to be print accurate because i will sum them don’t have to be printf
can be bc or other thing as long as i can put in bash script is fine

try

printf "%Xn" $((0x349b84b6431a6c4ef1 + 1))
9B84B6431A6C4EF2

expecting

printf "%Xn" $((0x349b84b6431a6c4ef1 + 1))
349B84B6431A6C4EF2