The noun is a hyphenated form check-in, to mean the act of checking into a room, or reporting in. When used as a verb to mean confirming or reporting, it is two words, to "check in."
Examples:
He had a late check-in for the flight.
They are expected to check in tomorrow.
checklist is one word
It is usually written as one word.
Yes.Checked out is the past tense of check out. Check out is a phrasal verb - it is more than one word. The two words check and out act together like one word.
one syllable
dictionary.com
There are two syllables. Check and mark are one syllable each.
One thousand one hundred and 00/100
It is commonly used as two words. When I tried it as one word, both my spell check and the spell check in the top right corner of this answer box marked it as misspelled.
There is not one. To the one who wrote 'There is not one', actually there is, the word is TYPEWRITER, 10 letters? Check. Using qwertyuiop? Check.
One thousand one hundred ninety-two and 00/100The word 'dollars' is usually already printed on the check
One hundred twenty and 00/100The word 'dollars' is usually already printed on the check
One hundred fifty thousand and 00/100 (the word 'dollars' will already be on the check).