This cookbook is one thousand yen.
That French person is a one-in-a-thousand genius.
I ate a thousand rice flour dumplings.
The kanji and the word are exactly the same. That means they share meanings as well.
Normally a single kanji making up a word like this means it will use the kun'yomi readings. Numbers are generally the exception, though, which means this word uses the on'yomi reading. If you learned the kanji, then you should already know this!