The centre of the Milky Way galaxy is about 26,000 light years, or roughly 245 quadrillion (245,000,000,000,000,000) kilometres. Our next closest galaxy is the Andromeda Galaxy, which is about 2.5 million light years away, or roughly 26,000,000,000,000,000,000 kilometres. The best estimate of the size of the observable universe (given that it has been expanding for 13.7 billion years), is about 156 billion light years (1,560,000,000,000,000,000,000,000 kilometres) across.
100,000 kilometres from the Earth (over a third of the way to the Moon, where there is absolutely no influence from the Earth’s atmosphere), there are around seven million particles per cubic metre. At the edge of the Solar System, the density is down to about a thousand atoms per cubic metre. In intergalactic space, there are only about ten atoms per cubic metre of space.
The fastest spinning pulsar known is PSR J1748-2446ad, it is less than 16km across, but just under twice the mass of the Sun. It is spinning at 70,000 km per second at its equator, 24% the speed of light