There are 6 natural numbers from 1 to 6 written on the six faces of a cube. If the cube is thrown upwards arbitrarily, what is the probability that the number facing up is a prime number after it falls?
一个正方体的六个面上分别写有1-6共6个自然数．把这个正方体任意上抛，落下后，朝上的数是质数的可能性是多少．
<gadget id="calculator">3 / 6</gadget>
<output>1/2 = around 0.5</output>

<result>1/2 = around 0.5</result>