I climbed Mt. Fuji on my sixteenth birthday.
There is an American who hasn't moved away from the entrance of Mt. Fuji for 16 years.
I am forever sixteen.
You have ten and six (not to be confused with six tens!). When you have ten and six, you have a total of sixteen.
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well!