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156 (one hundred [and] fifty-six) is the natural number, following 155 and preceding 157.

In mathematics

156 is the number of graphs on 6 unlabeled nodes.^[2]

156 is a repdigit in base 5 (1111), and also in bases 25, 38, 51, 77, and 155.

Convoy HX-156 was the 156th of the numbered series of World War II HX convoys of merchant ships from Halifax, Nova Scotia to Liverpool during World War II
The Fieseler Fi 156 Storch was a small German liaison aircraft during World War II
The German submarine U-156
USNS Bull Run (T-AO-156) was a United States Navy T2 tanker during World War II
USS Alamosa (AK-156) was a United States Navy cargo ship during World War II
USS Captivate (AM-156) was a United States Navy Admirable-class minesweeper during World War II
USS City of Dalhart (IX-156) was a United States Navy ship during World War II
USS General D. E. Aultman (AP-156) was a United States Navy General G. O. Squier-class transport during World War II
USS J. Fred Talbott (DD-156) was a United States Navy Wickes-class destroyer during World War II
USS Luiseno (ATF-156) was a United States Navy Abnaki-class tug during World War II
USS Mellette (APA-156) was a United States Navy Haskell-class attack transport during World War II
USS Reeves (DE-156) was a United States Navy Buckley-class destroyer escort during World War II
USS Winchester (SP-156) was a United States Navy fast civilian yacht during World War I

156, a song by the Danish rock band Mew appearing in both their 2000 album Half the World Is Watching Me and their 2003 album Frengers.
NM 156, a 1984 song by the heavy metal band Queensrÿche from the album The Warning
156, a song by the Polish Black Metal band Blaze of Perdition from the 2010 album Towards the Blaze of Perdition

The Alfa Romeo 156 car produced from 1997 to 2006.
The Ferrari 156 was a racecar made by Ferrari from 1961 to 1963.
The Ferrari 156/85 was a Formula One car in the 1985 Formula One season.
The Class 156 "Super Sprinter" DMU train.
The Midland Railway 156 Class, a 2-4-0 tender engine built in the United Kingdom between 1866 and 1874.
London Buses route 156.
Martin 156, known as the Russian clipper, was a large flying boat aircraft intended for transoceanic service.

156 is also:

The year AD 156 or 156 BC
156 AH is a year in the Islamic calendar that corresponds to 772 – 773 CE
156 Xanthippe is a main belt asteroid with a dark surface
The number of hourly gongs a clock strikes in one day (78 AM gongs and 78 PM gongs)
The number of sons of Magbish in the Census of the men of Israel upon return from exile (Bible, Ezra 2:30)
United States DS-156 visa issued for U.S. Department of State Nonimmigrant Visa Application
The atomic number of an element temporarily called Unpenthexium.^[3]
The Indian Head No. 156, Saskatchewan rural municipality in the Canadian province of Saskatchewan