Q:

Can you open this vault? 

Your rich and famous riddler friend has frequent memory loss since he's getting older and older. 
In order to prevent himself from forgetting everything, he writes everything as a riddle in his diary, and 
he has all his goods placed in different vaults.  One morning, he wants to show you the 
brand new watch he bought the day before.  Both of you go in the vaults room.  The old riddler then gives you
his diary, approaches the vaults and tells you : 

"Mmh, let's see the vault's number." 

You open his diary under the section "Jewels & Watches", and read out loud:

"The number of the vault is a four digits number : there's nothing between you and I."

Your friend mumble:

"An easy one to start, obviously.  Alright, and the combination, please?  The corresponding riddle might be right under the first one." 

And indeed, it is. 

To find the combination, you will need to fill the blanks of the following sentence by numbers, which put side by side, will help you open the vault. 
   But be careful, the final sentence has to make sense...
This sentence must have ________ vowels and ________ consonants. 

You see your friend thinking, and after a couple of minutes, he says:

"Damn, this one is harder than I thought.  I don't know if you will see my new wristwatch today, my friend..."

Confidently, you reassure him:

"Don't worry, I know exactly the combination!" 

So, what is the vault's number and what is its combination? 

A:

The vault number could be:

 2109 - credits @AndrewF

And the combination is:

 2138

 Because the sentence
 "This sentence must have twenty-one vowels and thirty-eight consonants." 
 Consists of 21 vowels and 38 consonants. 

 P.S. Assuming letter Y is a vowel. 

A:

A shot in the dark here
"The number of the vault is a four digits number : there's nothing between you and I."

 2109  U is the 21st letter of the alphabet and i is the 9th

This sentence must have ________ vowels and ________ consonants. 

 2138 assuming y as a vowel from Gintas K, can find nothing else that fits

