Number 81
Number 81 spell 🔊, write in words: eightyone . Ordinal number 81th is said 🔊 and write: eightyfirst. Phone prefix +81 or 0081. The meaning of number 81 in Maths: Is Prime? Factorization and dividers. The square root and cube root of 81. The meaning in computer science, numerology, codes and images, writing and naming in other languages, other interesting facts, news.
Useful information about number 81
The number 81 converted to a Mayan number is  
Decimal and Mayan number conversions. 
Weight conversion
81 kilograms (kg) = 178.6 pounds (lb)
81 pounds (lb) = 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:
Images of the number  
Image (1) of the number  Image (2) of the number 
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Number 81 infographic.

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Photo of number 81
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 official 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 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).
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 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).
Calculator
81  
Advanced math operations
Is Prime?
The number 81 is not a prime number. The closest prime numbers are 79, 83.
81th prime number in order is 419.
Factorization and dividers
Factorization 3 * 3 * 3 * 3 = 81
Divisors of number 81 are 1 , 3 , 9 , 27 , 81
Total Divisors 5.
Sum of Divisors 121.
Powers
The second power of 81^{2} is 6.561.
The third power of 81^{3} is 531.441.
Roots
The square root √81 is 9 raíz cuadrada exacta.
The cube root of ^{3}√81 is 4,326749.
Logarithms
The natural logarithm of No. ln 81 = log_{e} 81 = 4,394449.
The logarithm to base 10 of No. log_{10} 81 = 1,908485.
The Napierian logarithm of No. log_{1/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.
Properties of the number 81
Is a Friedman number: NoIs a Fibonacci number: No
Is a Bell number: No
Is a palindromic number: No
Is a pentagonal number: No
Is a perfect number: No
Number 81 in Computer Science
Code type  Code value 

Port 81/TCP  Torpark  Onion routing ORport 
Ascii  81 ascii is character Q 
Unix time  Unix time 81 is equal to Thursday Jan. 1, 1970, 12:01:21 a.m. GMT 
IPv4, IPv6  Number 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 BASE64  ODE= 
81 MD5  43ec517d68b6edd3015b3edc9a11367b 
81 SHA1  1d513c0bcbe33b2e7440e5e14d0b22ef95c9d673 
81 SHA224  0334eec4a00b1fbc7fcf4225707609c926a23a8c77b4def29fd71006 
81 SHA256  5316ca1c5ddca8e6ceccfce58f3b8540e540ee22f6180fb89492904051b3d531 
81 SHA384  456d0ef673c9975197784ab352c2d9a9801185cdec3b1c449482b13d4b5bc9220735b37747fee9feaebbc5d1c3286fd0 
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Numerology 81
The meaning of the number 8 (eight), numerology 8
Character frequency 8: 1
The meaning of the number 1 (one), numerology 1
Character frequency 1: 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).
 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).
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
Please write us
If you know something interesting about the number 81 or any natural number (positive integer), please write to us.Number 81 in other languages
Spanish:  🔊 (número 81)  ochenta y uno 
German:  🔊 (Anzahl 81)  einundachtzig 
French:  🔊 (nombre 81)  quatrevingtun 
Portuguese:  🔊 (número 81)  oitenta e um 
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)  שמנים ואחד 
Dutch:  🔊 (nummer 81)  eenentachtig 
Japanese:  🔊 (数 81)  八十一 
Indonesian:  🔊 (jumlah 81)  delapan puluh satu 
Italian:  🔊 (numero 81)  ottantuno 
Norwegian:  🔊 (nummer 81)  åttien 
Polish:  🔊 (liczba 81)  osiemdziesiąt jeden 
Russian:  🔊 (номер 81)  восемьдесят один 
Turkish:  🔊 (numara 81)  seksenbir 
Thai:  🔊 (จำนวน 81)  แปดสิบเอ็ด 
Ukrainian:  🔊 (номер 81)  вiсiмдесят одна 
Vietnamese:  🔊 (con số 81)  tám mươi mốt 
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Number 81 in News
BBC: EnglandIndia Test finely poised after seesaw day
Ollie Pope strikes 81 and Chris Woakes 50 but England's fourth Test against India remains tantalisingly poised after a seesaw second day at The Kia Oval. Sept. 3, 2021 
BBC: England v India: Shardul Thakur removes Ollie Pope to give India pivotal wicket.
England's Ollie Pope misses out on a second career Test century, chopping onto his own stumps from Shardul Thakur on 81 during the fourth Test at the Oval. Sept. 3, 2021 
NyTimes: A Women’s March in Mexico City Turns Violent, With at Least 81 Injured
Armed with blowtorches and hammers, women demonstrated at the president’s residence, demanding that Mexico’s government take action to address one of the world’s worst rates of gender violence. March 9, 2021 