No 1 :

The Number 1 is reserved for the current world champion, as an option for them to use while they defend the championship throughout the subsequent season. 

They are not obligated to use No 1, but if they do, their number remains their property. 

For example, Lewis Hamilton chose to wear his 44 while defending his championships but Max Verstappen has adorned the front of his 2022 machine with the No 1. 

Andrew Burden

The author Kiwi F1 Fan