It's about 15,000,000,000 times as wide as a Glucose Molecule
In other words, 21 meters is 14,000,000,000 times the width of a Glucose Molecule, and the width of a Glucose Molecule is 0.000000000071 times that amount.(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.
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 0.0000000893 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 10,000,000 times as long as a Bacterium
In other words, 21 meters is 11,000,000 times the length of a Bacterium, and the length of a Bacterium is 0.000000091 times that amount.(Escherichia coli) (rod-shaped configuration)
An rod-shaped E. coli bacterium measures about 0.00000200 meters in length. A staple of biology labs, E. coli can reproduce in as little as twenty minutes.
It's about 3,500,000 times as long as a Cell's Nucleus
In other words, 21 meters is 3,500,000 times the length of a Cell's Nucleus, and the length of a Cell's Nucleus is 0.00000029 times that amount.(for animal cell)
The nucleus of an animal cell measures an average of 0.00000600 meters. The nucleus is the largest organelle in these cells, accounting for about 10% of the cell's total volume.
It's about 3,000,000 times as long as a Red Blood Cell
In other words, 21 meters is 2,800,000 times the length of a Red Blood Cell, and the length of a Red Blood Cell is 0.00000036 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 200,000 times as wide as a Strand of Hair
In other words, 21 meters is 210,000 times the width of a Strand of Hair, and the width of a Strand of Hair is 0.0000048 times that amount.(average)
A strand of human hair averages 99 µm (micrometers), with blond hair being the finest and black hair the thickest. On a healthy scalp, each strand of hair will last up to 6 years.
It's about 200,000 times as tall as a sheet of Paper
In other words, 21 meters is 200,000 times the height of a sheet of Paper, and the height of a sheet of Paper is 0.0000050 times that amount.(for US Letter, a.k.a. ANSI A; 215.9mm by 279.4mm (8.5 in x 11 in); 20lb)
A single sheet of 20 lb, 8.5 inch x 11 inch paper is just 0.0001 meters thick. This style of paper weighs a mere 5 g per sheet.