173 (one hundred [and] seventy-three) is the natural number following 172 and preceding 174.

173 is:

• an odd number.
• a deficient number.
• an odious number.
• a balanced prime.^[1]
• an Eisenstein prime with no imaginary part.
• a Sophie Germain prime.^[2]
• an inconsummate number.^[3]
• the sum of 2 squares: 2² + 13².
• the sum of three consecutive prime numbers: 53 + 59 + 61.
• Palindromic number in bases 3 (20102₃) and 9 (212₉).
• the 40th prime number following 167 and preceding 179.

• 173 Ino is a large dark main belt asteroid
• 173P/Mueller is a periodic comet in the Solar System
• Arp 173 (VV 296, KPG 439) is a pair of galaxies in the constellation Boötes

• 173rd Air Refueling Squadron unit of the Nebraska Air National Guard
• 173rd Airborne Brigade Combat Team of the United States Army based in Vicenza
• 173rd Battalion unit of the Canadian Expeditionary Force during the World War I
• 173rd Special Operations Aviation Squadron of the Australian Army
• K-173 Chelyabinsk Russian Oscar-class submarine
• USNS Provo (T-AG-173) was a U.S. Navy Phoenix-class auxiliary ship following World War II
• USS Codington (AK-173) was a U.S. Navy Alamosa-class cargo ship during World War II
• USS Eldridge (DE-173) was a U.S. Navy Cannon-class destroyer escort during World War II
• USS Etamin (IX-173) was a U.S. Navy Crater-class cargo ship during World War II
• USS Florence (SP-173) was a U.S. Navy yacht during World War I
• USS Hyde (APA-173) was a U.S. Navy Haskell-class attack transport ship during World War II
• USS PC-472 was a 173-foot (53 m) U.S. Navy submarine chaser during World War II
• USS Pike (SS-173) was a U.S. Navy Porpoise-class submarine during World War II
• USS Sproston (DD-173) was a U.S. Navy Wickes-class destroyer following World War II
• Vought V-173 (Flying Pancake) was a U.S. Navy experimental test aircraft during World War II

• The Georgia Railroad, the world longest railroad in 1845, ran for 173 miles (278 km) from Augusta to Marthasville (Atlanta, Georgia)
• United Airlines Flight 173 en route from Denver to Portland crashed on December 28, 1978
• The Velocity 173 was a kit aircraft produced by Velocity Aircraft in the early 1990s.

• The book 173 Hours in Captivity (2000)
• SCP-173, a fictional statue

173 is also:

• The year AD 173 or 173 BC
• 173 AH is a year in the Islamic calendar that corresponds to 789 – 790 CE
• The atomic number of an element temporarily called unsepttrium
• Topic of discussion during the podcast "Skeptics with a K" episode 180 ^[4]

• List of highways numbered 173
• United Nations Security Council Resolution 173
• United States Supreme Court cases, Volume 173

Wikimedia Commons has media related to 173 (number).

• Number Facts and Trivia: 173
• Prime curiosities: 173
• Number Gossip: 173