Site administrators
From MoodleDocs
Site administrators have permissions to do anything.
Users may be assigned the role of site administrator by another site administrator in Administration > Site administration > Users > Permissions > Site administrators, but the role itself cannot be edited (or deleted!).
Note: The primary administrator (created when the site was created) cannot be removed from the site administrator role.
Note: When using MNet, see MNet#Assigning_the_role_of_admin