Number: 21

Facts about the number: 21 is the number of points required to win a game in badminton and table tennis (before 2001). 21 is the number of trump cards of the tarot deck if one does not consider The Fool to be a proper trump card. 21 is the number of demands which were sent to the Chinese government by the Japanese government of Okuma Shigenobu in 1915. 21 is the smallest natural number that is not close to a power of 2, 2^n, where the range of closeness is +- n. 21 is the smallest number of distinct squares needed to tile a square. 21 is the fifth discrete Semiprime and the second in the (3.q) family. 21 is the smallest number of differently sized squares needed to square the square.
The number of digits in the number: \( n \): \( d = \lfloor \log_{10}(n) \rfloor + 1 \)	2
Sum of the digits: \( n \): \( S = \sum_{i=1}^{k} d_i \)	3
Reverse number: \( \text{Reverse}(n) = \sum_{i=1}^{k} d_i \cdot 10^{k-i} \)	0.047619047619048
Binary number system: \( n = \sum_{i=0}^{k-1} d_i \cdot 2^i \)	10101
Hexadecimal number system: \( n = \sum_{i=0}^{k-1} d_i \cdot 16^i \)	15
Parity of the number: \( \text{Parity}(n) = n \mod 2 \)	odd
Simplicity of the number: \(\text{IsPrime}(n) = n > 1 \land \forall d \in [2, \sqrt{n}], n \mod d \neq 0\)	false
The square root: \(\sqrt{n} = n^{\frac{1}{2}}\)	4.5825756949558
The factorial of the number: \( n!=n \times (n-1) \times (n-2) \times \ldots \times 2 \times 1 \)	5.1090942171709E+19
The sign of the number: \(\text{sign}(n) = \begin{cases} 1, & \text{if } n>0 \ 0, & \text{if } n=0 \ -1, & \text{if } n<0 \end{cases}\)	+
The nearest multiple of 10: \(\text{10}(n) = 10 \times \left\lfloor \frac{n + 5}{10} \right\rfloor\)	0
The nearest multiple of 100: \(\text{100}(n) = 100 \times \left\lfloor \frac{n + 50}{100} \right\rfloor\)	0
Sine: \(\sin(x) = \sum_{n=0}^{\infty} \frac{(-1)^n x^{2n+1}}{(2n+1)!}\)	0.83665563853606
Cosine: \(\cos(x) = \sum_{n=0}^{\infty} \frac{(-1)^n x^{2n}}{(2n)!}\)	-0.54772926022427
Tangent: \(\tan(x) = \sum_{n=0}^{\infty} \frac{(-1)^n 2^{2n} (2^{2n} - 1) B_{2n} x^{2n-1}}{(2n)!}\)	-1.5274985276366
The square of the number: \(\text{square}(n) = n^2\)	441
Cubic root: \(\text{}(n) = \sqrt[3]{n}\)	2.7589241763811
Natural logarithm: \(\ln(ab) = \ln(a) + \ln(b)\)	3.0445224377234
Common logarithm: \(\log_{10}(ab) = \log_{10}(a) + \log_{10}(b)\)	1.3222192947339
All divisors of a number: \( D(n) = \{ d \in \mathbb{Z}^+ : n \mod d = 0 \} \)	1, 3, 7, 21
Base64:	MjE=
SHA1:	472b07b9fcf2c2451e8781e944bf5f77cd8457c8
MD5:	3c59dc048e8850243be8079a5c74d079
Converts a number to a Roman representation:	XXI
Converting the number of seconds to days, hours, minutes and seconds:	days: 0, hours: 0, minutes: 0, seconds: 21.
Converts a number to a date in UNIX time format:
	Chinese:	1970 月 1 星期四
	Spanish:	1970 Enero 1 Jueves
	English:	1970 January 1 Thursday
	Hindi:	1970 जनवरी 1 गुरुवार
	Arab:	1970 يناير 1 الخميس
	Bengal:	1970 জানুয়ারী 1 বৃহস্পতিবার
	Portuguese:	1970 Janeiro 1 Quinta-feira
	Russian:	1970 Январь 1 Четверг
	Japanese:	1970 一月 1 木曜日
	Lahnda:	1970 جنوری 1 جمعرات
	Marathi:	1970 जानेवारी 1 गुरुवार
	Telugu:	1970 జనవరి 1 గురువారం
	Malay:	1970 Januari 1 Khamis
	Turkish:	1970 Ocak 1 Perşembe
	Korean:	1970 1월 1 목요일
	French:	1970 Janvier 1 Jeudi
	German:	1970 Januar 1 Donnerstag
	Vietnamese:	1970 Tháng Một 1 Thứ năm
	Tamil:	1970 ஜனவரி 1 வியாழக்கிழமை
	Urdu:	1970 جنوری 1 جمعرات
	Javanese:	1970 Januari 1 Kemis
	Italian:	1970 Gennaio 1 Giovedì
	Persian:	1970 ژانویه 1 پنج‌شنبه
	Gujaratis:	1970 જાન્યુઆરી 1 ગુરુવાર
Length:
	21 kilometers = 21,000.00 meters
	21 miles = 33,796.14 meters
	21 feet = 6.40 meters
	21 inches = 0.53 meters
	21 yards = 19.20 meters
	21 meters = 0.02 kilometers
	21 meters = 0.01 miles
	21 meters = 68.90 feet
	21 meters = 826.77 inches
	21 meters = 22.97 yards
Weight:
	21 pounds = 9.53 kilograms
	21 grams = 0.02 kilograms
	21 ounces = 0.60 kilograms
	21 tons = 19,050.89 kilograms
	21 kilograms = 46.30 pounds
	21 kilograms = 21,000.00 grams
	21 kilograms = 740.75 ounces
	21 kilograms = 0.02 tons
Volume:
	21 gallons = 79.49 liters
	21 milliliters = 0.02 liters
	21 cubic meters = 21,000.00 liters
	21 liters = 5.55 gallons
	21 liters = 21,000.00 milliliters
	21 liters = 0.02 cubic meters
Area:
	21 acres = 84,984.06 square meters
	21 hectares = 210,000.00 square meters
	21 square feet = 1.95 square meters
	21 square inches = 0.01 square meters
	21 square meters = 0.01 acres
	21 square meters = 0.00 hectares
	21 square meters = 226.04 square feet
	21 square meters = 32,550.07 square inches
Temperature:
	21 celsius = 69.80 fahrenheit
	21 celsius = 294.15 kelvin
	21 fahrenheit = -6.11 celsius
	21 fahrenheit = 267.04 kelvin
	21 kelvin = -252.15 celsius
	21 kelvin = -421.87 fahrenheit
Time:
	21 seconds = 0.35 minutes
	21 seconds = 0.01 hours
	21 seconds = 0.00 days
	21 minutes = 1,260.00 seconds
	21 minutes = 0.35 hours
	21 minutes = 0.01 days
	21 hours = 75,600.00 seconds
	21 hours = 1,260.00 minutes
	21 hours = 0.88 days
	21 days = 1,814,400.00 seconds
	21 days = 30,240.00 minutes
	21 days = 504.00 hours
Energy:
	21 joules = 5.02 calories
	21 joules = 0.02 kilojoules
	21 joules = 0.01 watt hours
	21 calories = 87.86 joules
	21 calories = 0.09 kilojoules
	21 kilojoules = 21,000.00 joules
	21 kilojoules = 5,019.13 calories
	21 watt hours = 75,600.00 joules
	21 watt hours = 75.60 kilojoules
Information:
	21 bytes = 0.02 kilobytes
	21 kilobytes = 21,504.00 bytes
	21 kilobytes = 0.02 megabytes
	21 megabytes = 21,504.00 kilobytes
	21 megabytes = 0.02 gigabytes
	21 gigabytes = 21,504.00 megabytes
	21 gigabytes = 0.02 terabytes
	21 terabytes = 21,504.00 gigabytes