It's about 550,000,000 times as long as a Grain of Sand.
In other words, 668 kilometers is 534,000,000 times the length of a Grain of Sand, and the length of a Grain of Sand is 0.000000001870 times that amount.(medium grain)
Composed mainly of quartz, mica, feldspar, or magnetite, a grain of sand measures an average of 0.000001250 kilometers. In 2007, a team of seven in Myrtle Beach created the world's tallest sandcastle, which measured 0.0151 kilometers in height.
It's about 6,500,000,000 times as long as a Strand of Hair.
It's about 6,500,000,000 times as tall as a Human hair, Strand of.
It's about 7,000,000,000 times as tall as a sheet of Paper.
It's about 90,000,000,000 times as long as a Red Blood Cell.
In other words, 668 kilometers is 89,000,000,000 times the length of a Red Blood Cell, and the length of a Red Blood Cell is 0.0000000000110 times that amount.(a.k.a. RBCs, a.k.a. haematids, a.k.a. erythrocyte, a.k.a. erythroid cells, a.k.a. red blood corpuscles) An average Red Blood Cell measures 7.5 µm (micrometers) in diameter. An average human has 20 - 30 trillion red blood cells in their body and each cell completes a circulatory lap in about 20 seconds.
It's about 100,000,000,000 times as long as a Nucleus (Cellular).
In other words, 668 kilometers is 110,000,000,000 times the length of a Nucleus (Cellular), and the length of a Nucleus (Cellular) is 0.00000000000910 times that amount.(for animal cell)
The nucleus of an animal cell measures an average of 0.00000000600 kilometers. The nucleus is the largest organelle in these cells, accounting for about 10% of the cell's total volume.
It's about 350,000,000,000 times as long as an E. coli Bacterium.
In other words, the length of an E. coli Bacterium is 0.00000000000300 times 668 kilometers.(Escherichia coli) (rod-shaped configuration)
An rod-shaped E. coli bacterium measures about 0.00000000200 kilometers in length. A staple of biology labs, E. coli can reproduce in as little as twenty minutes.