The word "deeded" contains only 2 letters that are each used three times within the word. It is the only such word in the English language.
Word "CORPORATION" has got 11 letters so we could arrange 11 letters in 11P11 ways=11! ways But, Letter 'O' and 'R' are repeating thrice and twice respectively. And, presence of duplicates reduces the chances of possible arrangements. Hence it will become, 11!/(2!*3!) [Since 'R' and 'O' are repeating twice and thrice respectively]