Mammoth Uncensored Word List:
13 words ending with n, 21 letters long

constitutionalization counterinterpretation disestablishmentarian overbureaucratization overcommercialization overindustrialisation overindustrialization quadragintacentillion quattuortrigintillion quinquanonagintillion quinquaoctogintillion quinquasexagintillion septuagintacentillion