npm can't be installed

shubham@shubham$ npm
The program 'npm' is currently not installed. You can install it by typing:
sudo apt-get install npm

shubham@shubham$ sudo apt-get install npm
Reading package lists... Done
Building dependency tree       
Reading state information... Done
npm is already the newest version.
0 upgraded, 0 newly installed, 0 to remove and 9 not upgraded.

shubham@shubham$ npm
The program 'npm' is currently not installed. You can install it by typing:
sudo apt-get install npm

shubham@shubham$ ls
Desktop    examples.desktop  Music      Pictures   tmp
Documents  firstProject      nohup.out  Public     Videos
Downloads  goibibo_ugc       npm        Templates  WebstormProjects

Based to all comments above, try this:

sudo apt-get autoclean
sudo apt-get update

sudo apt-get dist-upgrade
sudo apt-get install npm