166 (one hundred [and] sixty-six) is the natural number following 165 and preceding 167.

166 is an even number and a composite number. It is a centered triangular number.^[1]

Given 166, the Mertens function returns 0. 166 is a Smith number in base 10.^[2]

• 166 Rhodope is a dark main belt asteroid, in the Adeona family of asteroids
• 166P/NEAT is a periodic comet and centaur in the outer Solar System
• HD 166 is the 6th magnitude star in the constellation Andromeda

• 166th Signal Photo Company was the official photo unit in the 89th Division of George Patton's Third Army in World War II
• Convoy ON-166 was the 166th of the numbered ON series of merchant ship convoys outbound from the British Isles to North America departing February 11, 1943
• Marine Medium Helicopter Squadron 166 is a United States Marine Corps helicopter
• USCGC Tamaroa (WMEC-166) was a United States Coast Guard cutter during World War II
• USS Alcedo (SP-166) was a United States Navy yacht. She was the first American vessel lost in World War I
• USS Baron (DE-166) was a United States Navy Cannon-class destroyer escort during World War II
• USS Bush (DD-166) was a United States Navy Wickes-class destroyer during the World War I
• USS Cabell (AK-166) was a United States Navy Alamosa-class cargo ship during World War II
• USS Fond du Lac (APA-166) was a United States Navy Haskell-class attack transport ship during World War II
• USS Jamestown (AGTR-3/AG-166) was a United States Navy Oxford-class technical research ship following World War II

• Sam Thompson’s 166 RBIs in 1887 stood as a Major League Baseball record until Babe Ruth broke the record in 1921

• British Rail Class 166
• The now-defunct elevated IRT Third Avenue Line, 166th Street station in the Bronx, New York
• London Buses route 166
• Piaggio P.166 is a twin-engined push prop-driven utility aircraft developed by the Italian aircraft manufacturer Piaggio
• Banat Air Flight 166 crashed on take-off en route from Romania on December 13, 1995
• Alfa Romeo 166 produced from 1998 to 2007
• Ferrari 166 model cars produced from 1948 to 1953
  • Ferrari 166 Inter (1949) Coachbuilt street coupe and cabriolet

166 is also:

• The year AD 166 or 166 BC
• The atomic number of an element temporarily called Unhexhexium

• List of highways numbered 166
• United States Supreme Court cases, Volume 166
• United Nations Security Council Resolution 166

Wikimedia Commons has media related to 166 (number).

• Number Facts and Trivia: 166
• The Number 166
• VirtueScience: 166 Archived 2011-06-07 at the Wayback Machine
• 166th Street (3rd Avenue El)