15, 19, 23, 32, 51, and 91 are written on the six sides of a cube. If the cube is thrown up arbitrarily, what is the probability that the number that faces up after falling is a composite number?
一个正方体的六个面上分别写着15、19、23、32、51、91，把这个正方体任意上抛，落下后朝上的数是合数的可能性是多少
<gadget id="calculator">4 / 6</gadget>
<output>2/3 = around 0.666667</output>

<result>2/3 = around 0.666667</result>