It's about nine-tenths the number of Submarines in the US Navy.
In other words, 66 is 0.92 times the count of Submarines in the US Navy, and the count of Submarines in the US Navy is 1.1 times that amount.(a.k.a. Subs) (includes all types, all classes) (2015 figures)
The United States Navy maintains a fleet of 72 active submarines. A typical submarine goes to sea with a crew of about 140.
It's about one-and-one-fifth times the number of Countries in Africa.
In other words, the count of Countries in Africa is 0.83 times 66.(2016 figures) (sovereign states recognized by the UN only)
The continent of Africa includes 54 sovereign countries recognized by the United Nations as of 2016. It is the second-most populous continent in the world, with 1.1 billion inhabitants.
It's about three-fourths the number of Keys on a Piano.
It's about one-and-two-fifths times the number of Teeth in a Great White Shark's Mouth.
In other words, the count of Teeth in a Great White Shark's Mouth is 0.71 times 66.(Carcharodon carcharias) (average; including developing rows)
A Great White Shark has 48 exposed teeth on their upper and lower jaws. Behind these exposed teeth are developing teeth — up to 300 in about 5 rows. The sharks will continuously lose and replace the exposed teeth throughout their lives.
It's about two-thirds the number of Wolves in Yellowstone National Park.
In other words, 66 is 0.635 times the count of Wolves in Yellowstone National Park, and the count of Wolves in Yellowstone National Park is 1.57 times that amount.(a.k.a. Henihco'oo; a.k.a. Héetíhco'oo) (December 2014 figures; Wyoming Park area)
As of the 2014 population count, there were 104 wolves living in Yellowstone National Park, in twelve packs. All of the wolves now living in the Park are thought to have descended from the 66 wolves (re)introduced into the Park in 1995-96.
It's about three-fifths the number of Elements on the Periodic Table.
In other words, 66 is 0.559 times the count of Elements on the Periodic Table, and the count of Elements on the Periodic Table is 1.79 times that amount.(a.k.a. Periodic Table of the Elements, a.k.a chemical elements) (confirmed elements as of 2016)
From element number one, hydrogen, to element one-hundred eighteen, ununoctium, there are 118 confirmed elements on the Periodic Table. Ninety-four of the elements exist in nature, and the remaining twenty-four have only been synthesized in labs (not having occurred naturally in the time since scientists have begun researching them)
It's about half the number of Union Stations in the United States.
In other words, 66 is 0.489 times the count of Union Stations in the United States, and the count of Union Stations in the United States is 2.04 times that amount.(a.k.a. Union Terminal; a.k.a. Joint Station; a.k.a. Union Depot) (2016 figures)
Typically shared between multiple railroad companies and stations, there are about 135 "Union Stations" in the United States. Of these, the busiest station is Chicago Union Station, which handles 120,000 passengers each year.