How many 11-letter words are there?

15,504 in the Tournament dictionary, which is the public-domain ENABLE word list. The Broad dictionary adds more.

What is the highest-scoring 11-letter word?

RAZZAMATAZZ at 49 points, counting tile values with no board multipliers.

No. The page shows the 300 highest-scoring; the pages linked below break the full list down by starting and ending letters.

15,504 words are exactly 11 letters long. RAZZAMATAZZ scores highest at 49 points.

Showing the highest-scoring of 15,504 words. The pages linked below split the rest into smaller lists.

Exactly 15,504 words in the dictionary run to 11 letters. The list starts with the ones that score best.

The results run from 11 letters up to 11, and the 11-letter group is the largest at 15,504 words.

For points rather than length, take RAZZAMATAZZ at 49 points. It tops both tables: 50 in Words With Friends as well.

Nothing here runs past 11 letters, where you will find RAZZAMATAZZ, QUIZZICALLY and HYDROXYZINE.

The related pages below slice this list more finely than one page usefully can.

quizzically: in a quizzical and questioning manner
hydroxyzine: a drug (trade names Atarax and Vistaril) used as a tranquilizer to treat anxiety and motion sickness
jabberwocky: nonsensical language (according to Lewis Carroll)
zygomorphic: capable of division into symmetrical halves by only one longitudinal plane passing through the axis
crackerjack: something excellent of its kind

How many 11-letter words are there?: 15,504 in the Tournament dictionary, which is the public-domain ENABLE word list. The Broad dictionary adds more.
What is the highest-scoring 11-letter word?: RAZZAMATAZZ at 49 points, counting tile values with no board multipliers.
Are all of them listed here?: No. The page shows the 300 highest-scoring; the pages linked below break the full list down by starting and ending letters.