Is Yamamoto’s phone number 612-7736?
Let's meet at Mt. Fuji at six o'clock.
Six times six is thirty-six, right?
The kanji and the word are exactly the same. That means they share meanings as well.
Since this word is made up of a single kanji, it should use the kun'yomi reading. Numbers, as you know, are the exception to this rule. They usually use the on'yomi reading, and the on'yomi reading is the one you learned along with this kanji, meaning you should be good to go!