[node.js] sudo: npm: command not found

I'm trying to upgrade to the latest version of node. I'm following the instructions at http://davidwalsh.name/upgrade-nodejs

But when I do:

sudo npm install -g n

I get the error:

sudo: npm: command not found

npm works without sudo. When I do:

whereis node

I see:

node: /usr/bin/node /usr/lib/node /usr/bin/X11/node /usr/local/node

Running:

which npm

Shows:

/usr/local/node/bin/npm

I tried the solution at https://stackoverflow.com/a/5062718/1246159

But I'm still getting the same error. I also looked at the /etc/sudoers file and the relevant line is:

Defaults        secure_path="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"

This looks fine to me. How can I possibly get NPM working with sudo command?

I had to do

sudo apt-get install npm

that worked for me.