I use two Softwares 1 for my PC ! for my Mobile device
For my PC I use Internet Download Manager (http://www.internetdownloadmanager.com/) which really works great for youtube video Download and not only that I can use it on other sites as well.
While for my Mobile Device I use Tubemate.apk (https://tubemate.en.uptodown.com/android) for android
which really works best for my phone and it does hangs up while downlaoding and I have loads of options in download format.