ubun2^beta

I ran ulimit -n and it is current showing as 1024. I want to increase my file limit from 1024 to 4084. So, i tried running the following command
 
sudo ulimit -n 2048
 
but i get the following error
 
sudo: ulimit: command not found
 
How to increase the file limit from 1024 to 4084. Any help will be appreciated.