Go grab a calculator and then divide the mass of Uranus (8.68 x 1025 kg) by the volume (6.83 x 1013 km3. If you did the math right, you should come out with the same value for the density of Uranus: 1.27 g/cm3. read more
Well, Uranus actually is the second least dense planet in the Solar System after Saturn. The density of Saturn is 0.687 g/cm 3. Earth is the densest planet in the Solar System, measuring 5.51 g/cm 3. read more
But Uranus doesn’t have the largest amount of mass in the solar system. Compared to the largest planet in the solar system, Jupiter, Uranus is a mere 1/20 of its mass. The density of Uranus is 1.27 grams/cubic centimeter. read more