Administrator, and more generally user management varies depending on the interface.
For Analyzer NX and the Analytics Suite 1, access rights are based on contracts and domains. It is not possible to have more than one administrator for each contract, as they are our administrative point of contact. However it is possible to create Power User profiles that have all the same permissions.
In the Analytics Suite 2, access rights are based on organisations that can contain several contracts as they were understood previously. This means it is now possible to have several administrators in one organisation, and create delegations to make the administration of the sites more flexible on a micro scale.
Here is the relevant documentation for the Analytics Suite 2: https://helpcentre.atinternet-solutions.com/hc/en-gb/sections/360000536764-Access-Rights