It's about 10,000,000 times as long as a Mitochondrion
In other words, 21 meters is 11,200,000 times the length of a Mitochondrion, and the length of a Mitochondrion is 0.00000008930 times that amount.(Eukaryotic; average)
A mitochondrion measures between 0.75 and 3 micrometers (Âµm). The mitochondrion is commonly referred to as the powerhouse of the cell, responsible for the generation of ATP. The size, shape, and distribution of mitochondria varies widely, with human liver cells each having 1,000 to 2,000 mitochondria.
It's about 0.00000006 times as long as The Distance from Earth to the Moon
In other words, 21 meters is 0.000000054625410 times the length of The Distance from Earth to the Moon, and the length of The Distance from Earth to the Moon is 18,306,500 times that amount.(a.k.a. Luna) (median of semi-major axis, or apigee, and semi-minor axes, or perigee)
The orbit of the Moon around the Earth is elliptical, with an average distance of 384,436,500 meters from center-to-center. About 428.376 kg of moon rock have been cataloged on the Earth, from the American Apollo and Soviet Luna Programs, and from samples that have been extracted from meteorites.
It's about 15,000,000,000 times as wide as a Glucose Molecule
In other words, the width of a Glucose Molecule is 0.0000000000710 times 21 meters.(C6H12O6, a.k.a. grape sugar) (open chain form)
Am individual glucose molecule measures 0.00000000150 meters in its open-chain form. Glucose is the most common fuel source of energy in human biology, with 3.75 kilocalories of energy per gram.