Why only outdated version of NPM is available on Debian/Ubuntu?

I’m using a Debian/Ubuntu based distribution (specifically, AWS Ubuntu 16.04) and trying to install NPM through apt-get.

My Angular 2 application needs a higher version than 3.9.x of NPM, but the default version which is getting installed is 3.5.2 using sudo apt-get install npm on AWS Ubuntu 16.04. I’m trying to update NPM, but it’s not getting upgraded to 4.6.1 (latest) from 3.5.2.

How do I install/update NPM so that I’ve got the latest version?

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