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131 (one hundred thirty-one) is the natural number following 130 and preceding 132.

In mathematics

131 is a Sophie Germain prime, an irregular prime, the second 3-digit palindromic prime, and also a permutable prime with 113 and 311. It can be expressed as the sum of three consecutive primes, 131 = 41 + 43 + 47. 131 is an Eisenstein prime with no imaginary part and real part of the form ${\displaystyle 3n-1}$. Because the next odd number, 133, is a semiprime, 131 is a Chen prime. 131 is an Ulam number.

131 is a full reptend prime in base 10 (and also in base 2). The decimal expansion of 1/131 repeats the digits 007633587786259541984732824427480916030534351145038167938931 297709923664122137404580152671755725190839694656488549618320 6106870229 indefinitely.

131 is the fifth discriminant of imaginary quadratic fields with class number 5, where the 131st prime number 739 is the fifteenth such discriminant. Meanwhile, there are conjectured to be a total of 131 discriminants of class number 8 (only one more discriminant could exist).

In the military

• Convair C-131 Samaritan was an American military transport produced from 1954 to 1956
• Strike Fighter Squadron (VFA-131) is a United States Navy F/A-18C Hornet fighter squadron stationed at Naval Air Station Oceana
• Tiger 131 is a German Tiger I heavy tank captured in Tunisia by the British 48th Royal Tank Regiment during World War II
• USNS Mission Santa Barbara (T-AO-131) was a Mission Buenaventura-class fleet oiler during World War II
• USS Bandera (APA-131) was a is a United States Navy Haskell-class attack transport ship during World War II
• USS Buchanan (DD-131) was a United States Navy Wickes-class destroyer
• USS General T. H. Bliss (AP-131) was a United States Navy General G. O. Squier-class transport ship during World War II
• USS Hammann (DE-131) was a United States Navy Edsall-class destroyer escort during World War II
• USS Melucta (AK-131) was a United States Navy Crater-class cargo ship during World War II
• USS Walter X. Young (APD-131) was a ship of the United States Navy during World War II
• ZIL-131 is a 3.5-ton 6x6 army truck

In transportation

• London Buses route 131 is a Transport for London contracted bus route in London
• The Fiat 131 Mirafiori small/medium family car produced from 1974 to 1984
• STS-131 is a NASA Contingency Logistic Flight (CLF) of the Space Shuttle Atlantis which launched in April 2010

In other fields

131 is also:

• The year AD 131 or 131 BC
• 131 AH is a year in the Islamic calendar that corresponds to 748 – 749 CE.
• 131 Vala is an inner main belt asteroid
• Iodine-131, or radioiodine, is a radioisotope of iodine for medical and pharmaceutical use
• ACP-131 is the controlling publication for listing of Q codes and Z codes, as published by NATO Allied countries
• Sonnet 131 by William Shakespeare
• 131 is the medical emergency telephone number in Chile
• United States Citizenship and Immigration Services Form I-131 to apply for a travel document, reentry permit, refugee travel document or advance parole
• 131 is the ID3v1 tag equivalent to Indie music

See also

• List of highways numbered 131
• United Nations Security Council Resolution 131

References

1. "Sloane's A005384 : Sophie Germain primes". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-05-27.
2. "Sloane's A000928 : Irregular primes". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-05-27.
3. "Ulam numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. 2016-04-18. Retrieved 2016-04-19.
4. Sloane, N. J. A. (ed.). "Sequence A046002 (Discriminants of imaginary quadratic fields with class number 5 (negated))". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2024-08-03.
5. Sloane, N. J. A. (ed.). "Sequence A046005 (Discriminants of imaginary quadratic fields with class number 8 (negated).)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2024-08-03.

• Integers