Number 81 facts

The odd number 81 is spelled 🔊, and written in words: eighty-one. The ordinal number 81st is said 🔊 and written as: eighty-first. Phone prefix +81 or 0081. The meaning of the number 81 in Maths: Is it Prime? Factorization and prime factors tree. The square root and cube root of 81. What is 81 in computer science, numerology, codes and images, writing and naming in other languages. Other interesting facts, videos, news related to 81.

What is 81 in other units

The decimal (Arabic) number 81 converted to a Roman number is LXXXI. Roman and decimal number conversions.
The number 81 converted to a Mayan number is mayan number 81
Decimal and Mayan number conversions.

Weight conversion


81 kilograms (kg) = 178.6 pounds (lbs)
81 pounds (lbs) = 36.7 kilograms (kg)

Length conversion


81 kilometers (km) equals to 50.331 miles (mi).
81 miles (mi) equals to 130.357 kilometers (km).
81 meters (m) equals to 130.357 feet (ft).
81 feet (ft) equals 24.689 meters (m).
81 centimeters (cm) equals to 31.9 inches (in).
81 inches (in) equals to 205.7 centimeters (cm).

Temperature conversion


81° Fahrenheit (°F) equals to 27.2° Celsius (°C)
81° Celsius (°C) equals to 177.8° Fahrenheit (°F)

Power conversion


81 Horsepower (hp) equals to 59.57 kilowatts (kW)
81 kilowatts (kW) equals to 110.14 horsepower (hp)

Time conversion

(hours, minutes, seconds, days, weeks)
81 seconds equals to 1 minute, 21 seconds
81 minutes equals to 1 hour, 21 minutes

Codes and images of the number 81

Number 81 morse code: ---.. .----
Sign language for number 81:
Sign language for number 81 Sign language for number 81
Number 81 in braille:
Number 81 in braille
Images of the number
Image (1) of the numberImage (2) of the number
Number 81 black image Number 81 red image
More images, other sizes, codes and colors ...

Number 81 infographic



Photo of number 81

Photo of the number 81

Year 81 AD

  • The Arch of Titus was constructed.
  • Empress Deng Sui was born.

Gregorian, Hebrew, Islamic, Persian and Buddhist Year (Calendar)

Gregorian year 81 is Buddhist year 624.
Buddhist year 81 is Gregorian year 462 a. C.
Gregorian year 81 is Islamic year -558 or -557.
Islamic year 81 is Gregorian year 700 or 701.
Gregorian year 81 is Persian year -542 or -541.
Persian year 81 is Gregorian 702 or 703.
Gregorian year 81 is Hebrew year 3841 or 3842.
Hebrew year 81 is Gregorian year 3679 a. C.
The Buddhist calendar is used in Sri Lanka, Cambodia, Laos, Thailand, and Burma. The Persian calendar is the official calendar in Iran and Afghanistan.

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Mathematics of no. 81

Multiplications

Multiplication table of 81


81 multiplied by two equals 162 (81 x 2 = 162).
81 multiplied by three equals 243 (81 x 3 = 243).
81 multiplied by four equals 324 (81 x 4 = 324).
81 multiplied by five equals 405 (81 x 5 = 405).
81 multiplied by six equals 486 (81 x 6 = 486).
81 multiplied by seven equals 567 (81 x 7 = 567).
81 multiplied by eight equals 648 (81 x 8 = 648).
81 multiplied by nine equals 729 (81 x 9 = 729).
show multiplications by 6, 7, 8, 9 ...

Fractions: decimal fraction and common fraction

Fraction table of 81


Half of 81 is 40,5 (81 / 2 = 40,5 = 40 1/2).
One third of 81 is 27 (81 / 3 = 27).
One quarter of 81 is 20,25 (81 / 4 = 20,25 = 20 1/4).
One fifth of 81 is 16,2 (81 / 5 = 16,2 = 16 1/5).
One sixth of 81 is 13,5 (81 / 6 = 13,5 = 13 1/2).
One seventh of 81 is 11,5714 (81 / 7 = 11,5714 = 11 4/7).
One eighth of 81 is 10,125 (81 / 8 = 10,125 = 10 1/8).
One ninth of 81 is 9 (81 / 9 = 9).
show fractions by 6, 7, 8, 9 ...

Calculator

81

Advanced math operations

Is Prime?


The number 81 is not a prime number. The closest prime numbers are 79, 83.
The 81st prime number in order is 419.

Factorization and factors (dividers)


The prime factors of 81 are 34 or 3^4 or 3**4
The factors of 81 are 1, 3, 9, 27, 81.
Total factors 5.
Sum of factors 121 (40).

Prime factor tree


Powers


The second power of 812 is 6.561.
The third power of 813 is 531.441.

Roots


The square root √81 is 9 exact square root.
The cube root of 381 is 4,326749.

Logarithms


The natural logarithm of No. ln 81 = loge 81 = 4,394449.
The logarithm to base 10 of No. log10 81 = 1,908485.
The Napierian logarithm of No. log1/e 81 = -4,394449.

Trigonometric functions

The cosine of 81 is 0,776686.
The sine of 81 is -0,629888.
The tangent of 81 is -0,810994.

Number 81 in Computer Science

Code typeCode value
Port 81/TCPTorpark - Onion routing ORport
ASCII HtmlQ Uppercase Q Q
(ISO 8859-1 Characters)
Unix timeUnix time 81 is equal to Thursday Jan. 1, 1970, 12:01:21 a.m. GMT
IPv4, IPv6Number 81 internet address in dotted format v4 0.0.0.81, v6 ::51
81 Decimal = 1010001 Binary
81 Decimal = 10000 Ternary
81 Decimal = 121 Octal
81 Decimal = 51 Hexadecimal (0x51 hex)
81 BASE64ODE=
81 MD543ec517d68b6edd3015b3edc9a11367b
81 SHA11d513c0bcbe33b2e7440e5e14d0b22ef95c9d673
81 SHA2240334eec4a00b1fbc7fcf4225707609c926a23a8c77b4def29fd71006
81 SHA2565316ca1c5ddca8e6ceccfce58f3b8540e540ee22f6180fb89492904051b3d531
81 SHA384456d0ef673c9975197784ab352c2d9a9801185cdec3b1c449482b13d4b5bc9220735b37747fee9feaebbc5d1c3286fd0
More SHA codes related to the number 81 ...

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Numerology 81

The meaning of the number 8 (eight), numerology 8

Character frequency 8: 1

The number eight (8) is the sign of organization, perseverance and control of energy to produce material and spiritual achievements. It represents the power of realization, abundance in the spiritual and material world. Sometimes it denotes a tendency to sacrifice but also to be unscrupulous.
More about the the number 8 (eight), numerology 8 ...

The meaning of the number 1 (one), numerology 1

Character frequency 1: 1

Number one (1) came to develop or balance creativity, independence, originality, self-reliance and confidence in the world. It reflects power, creative strength, quick mind, drive and ambition. It is the sign of individualistic and aggressive nature.
More about the the number 1 (one), numerology 1 ...

Interesting facts about the number 81

Asteroids

  • (81) Terpsichore is asteroid number 81. It was discovered by E. W. L. Tempel from Marseille Observatory on 9/30/1864.

Areas, mountains and surfaces

  • The total area of Puerto Rico (main island) is 3,500 square miles (9,100 square km). Country Puerto Rico, insular area of the United States. 81th largest island in the world.

Distances between cities

  • There is a 81 miles (130 km) direct distance between Budta (Philippines) and Davao (Philippines).
  • There is a 51 miles (81 km) direct distance between Erbil (Iraq) and Mosul (Iraq).
  • There is a 81 miles (130 km) direct distance between Guangzhou (China) and Kowloon (Hong Kong).
  • There is a 81 miles (130 km) direct distance between Hāora (India) and Khulna (Bangladesh).
  • More distances between cities ...
  • There is a 81 miles (130 km) direct distance between Luoyang (China) and Pingdingshan (China).
  • There is a 81 miles (129 km) direct distance between New York City (USA) and Philadelphia (USA).
  • There is a 81 miles (129 km) direct distance between Santiago de los Caballeros (Dominican republic) and Santo Domingo (Dominican republic).

History and politics

  • United Nations Security Council Resolution number 81, adopted 24 May 1950. General Assembly Resolution 258. Resolution text.

Mathematics

  • 81 is the square of the sum of its digits.

Mobile and telephony

  • Number 81 or +81 or 0081 is a dial the international call prefix for Japan. (00/+) is dial the international call prefix.

Science

  • Thallium is the chemical element in the periodic table that has the symbol Tl and atomic number 81.

Sports

  • The best athletes to wear number 81
    Terrell Owens, NFL; Tim Brown, NFL; Dick "Night Train" Lane, NFL; Doug Atkins, NFL; Art Monk, NFL; Carl Eller, NFL

Tv, movies and cinematography

  • Archive 81 | Official Trailer | Netflix

№ 81 in other languages

How to say or write the number eighty-one in Spanish, German, French and other languages.
Spanish: 🔊 (número 81)

ochenta y uno

German: 🔊 (Nummer 81)

einundachtzig

French: 🔊 (nombre 81)

quatre-vingt-un

Portuguese: 🔊 (número 81)

oitenta e um

Hindi: 🔊 (संख्या 81)

इक्यासी

Chinese: 🔊 (数 81)

八十一

Arabian: 🔊 (عدد 81)

واحد و ثمانون

Czech: 🔊 (číslo 81)

osmdesát jedna

Korean: 🔊 (번호 81)

팔십일

Danish: 🔊 (nummer 81)

enogfirs

Hebrew: (מספר 81)

שמונים ואחת

Dutch: 🔊 (nummer 81)

eenentachtig

Japanese: 🔊 (数 81)

八十一

Indonesian: 🔊 (jumlah 81)

delapan puluh satu

Italian: 🔊 (numero 81)

ottantuno

Norwegian: 🔊 (nummer 81)

åtti-en

Polish: 🔊 (liczba 81)

osiemdziesiąt jeden

Russian: 🔊 (номер 81)

восемьдесят один

Turkish: 🔊 (numara 81)

seksenbir

Thai: 🔊 (จำนวน 81)

แปดสิบเอ็ด

Ukrainian: 🔊 (номер 81)

вісімдесят один

Vietnamese: 🔊 (con số 81)

tám mươi mốt

Other languages ...

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Frequently asked questions about the number 81

  • How do you write the number 81 in words?

    81 can be written as "eighty-one".

Number 81 in News

The Sydney Morning Herald: Rubble from 81 million kilometres away: Capsule carrying asteroid secrets lands on Earth
Asteroid samples fetched from deep space have parachuted into the Utah desert to cap a seven-year journey.
Sept. 25, 2023
France24: Saudi Arabia executes record 81 people in one day for terrorism-related offences
Saudi Arabia said Saturday it had executed a record 81 people in one day for terrorism-related offences, exceeding the total number killed last year and sparking criticism from rights activists.
March 13, 2022
The Sydney Morning Herald: Mass execution in Saudi Arabia as 81 people put to death
The executions come at a time of heightened concern over Saudi Arabia’s human rights record, but also as the West scrambles to replace its dependence on Russian oil.
March 13, 2022
BBC: Saudi Arabia executes 81 men in one day
The range of charges on which the men were convicted included terrorism and holding "deviant beliefs".
March 12, 2022
NyTimes: American Voters Now View Ukraine as Favorably as France, Germany and Japan
In a new survey, 81 percent of Americans say Ukraine is either friendly or an ally, a figure that rivals or exceeds that of many longtime U.S. allies.
March 12, 2022

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