Since I use El Capitan my Apple numeric keyboard doesn't work properly

Since I use El Capitan my Apple numeric keyboard doesn't work properly: those 5 keys don't work anymore (see screenshot below).

I tried restarting my computer, replugging the keyboard, and I checked all the steps from the Apple's help pages.

My computer is updated with the last released updates.

When I click on those 5 keys on my keyboard, they don't highlight on the onscreen keyboard viewer.

They worked very fine until the El Capitan update. The keyboard has not been shaken or hit in the meanwhile.

All the other keys work fine.

Any idea?