When 十 is pronounced とお?

[Lomaster]

The only time i hear japanese say とお is phone numbers (like ひゃくとお番)
What are other common usages of とお?

I've also got a sub-question, but don't want to post a new thread so i'll just ask here. As i understand it -つ counting is only used from 1 to 9. What if i need to use it further? (like if i don't know the correct counter for some stuff) For now i stick to 個（こ）like じゅうにこ, is there any other way?

 

[nekojita]

十日 (とおか) is the one that immediately comes to mind.

 

[Toritoribe]

Another similar example is 十月[とつき].

As i understand it -つ counting is only used from 1 to 9. What if i need to use it further? (like if i don't know the correct counter for some stuff) For now i stick to 個（こ）like じゅうにこ, is there any other way?

Just say only the number without any counters.
e.g.
タンスが１２[じゅうに]ある。

 

[Lomaster]

Seems like the use of とお is really limited. And thanks for clearing my sub-question up.