develop1 - 2013-12-29

Glad you were able to discover the corruptoin and reconstruct the correct password.
You may wish to reconsider having a 21 digit master that you do not "know". The length seems like overkill and not knowing your master puts you at risk of losing access to your keepass database.

It seems you would be much better served doing something else.
One option is to create a sentence that is always true regardless of the passage of time/circumstances/likes/dislikes/births/deaths/marriages/politics.

For example:
"my sister Jenny was born 3 years before my bother Hank"
this sentence is an easy way to construct the string:
msJwb3ybmbH

Most people would say 11 chars of "randomized" lowers/uppers/numbers is plenty strong and possibly faster than using another program to obtain your master key.

If you use keepass often then you will end up repeating that sentence in your brain so much I doubt you will ever forget your sentence.

You do want to make backups of your master key. You should be 100% sure that you never lose access. Do whatever can be done within in your circumstances. some might say that even masking tape to the underside of your bed frame is more preferable than losing access.