Every ten years from 1821-1911 there was a census in Ireland but unforunately 1st complete census is 1901.
The 1851 and 1841 census were used to verify ages for Old Age Pension claims at the start as claimants (supposed to be over 70 years old) were born before the start of civil registration of births (1864). Some extracts from 1841 + 1851 survive on pension claim forms.
The statistical data from each census was retained by the goverment as far as I know and probably is available (population of each townland, number of males and females, religious breakdown).
