This unique shape is a 7 sided die.
It's a lat-long polyisohedron, an order 3 polyisohedron. Though this shape has 21 sides, only 7 of them are stable, each of which appear with equal probability. The numbered sides are offset from the other sides so it's easy to read the result of a roll.
For more information on unique dice shapes, see http://loki3.com/poly/fair-dice.html.