Getting started- sudo npm install -g cordova, uid must be an unsigned int

Hi, I am new to ionic and new to development. I’m just following the guide to install ionic, but I can’t get past installing cordova.

I get the following error:
npm WARN deprecated minimatch@2.0.10: Please update to minimatch 3.0.2 or higher to avoid a RegExp DoS issue
npm ERR! Darwin 15.6.0
npm ERR! argv “/usr/local/bin/node” “/usr/local/bin/npm” “install” “-g” "cordova"
npm ERR! node v6.6.0
npm ERR! npm v3.10.8

npm ERR! uid must be an unsigned int

I am using:
Mac OS X El Capitan 10.11.6
just installed homebrew yesterday

Is there anything else I should have installed prior to getting started? Should I be using a different version of node or npm?