21
Number 21 (twenty-one) is an odd two-digits composite number and natural number following 20 and preceding 22.
| Nominal | 21 |
| Cardinal | twenty-one |
| Ordinal | 21st |
| Number of digits | 2 |
| Sum of digits | 3 |
| Product of digits | 2 |
| Number parity | Odd |
Calculation was done in 0.0000338554 seconds
| Prime factorization | 3 x 7 |
| Prime factors | 3, 7 |
| Number of distinct prime factors ω(n) | 2 |
| Total number of prime factors Ω(n) | 2 |
| Sum of prime factors | 10 |
| Product of prime factors | 21 |
Calculation was done in 0.0000081062 seconds
| List of proper divisors | 1, 3, 7 |
| List of all dividers | 1, 3, 7, 21 |
| Number of divisors d(n) | 4 |
| Sum of all divisors σ(n) | 32 |
| Aliquot sum | 11 |
| 21 is a deficient number , since it is larger than the sum of its proper divisors (11). Its deficiency is 10. |
Calculation was done in 0.0000269413 seconds
| Is 21 a prime number? | No |
| Is 21 a semiprime number? | Yes |
| Is 21 a Chen prime number? | No |
| Is 21 a Mersenne prime number? | No |
Calculation was done in 0.0000109673 seconds
| Is 21 a Catalan number? | No |
| Is 21 a Fibonacci number? | Yes |
| Is 21 a Idoneal number? | Yes: I15 |
Calculation was done in 0.0000028610 seconds
| 21 is not a Happy number |
| 21 is a Humble number |
| 21 is not a Münchhausen number |
| 21 is not a Perfect number |
| 21 is not a Perfect square |
| 21 is not a Palindrome |
Calculation was done in 0.0062370300 seconds
| Base | System | Value |
|---|
| 2 | Binary | 101012 |
| 3 | Ternary | 2103 |
| 4 | Quaternary | 1114 |
| 5 | Quinary | 415 |
| 6 | Senary | 336 |
| 7 | Septenary | 307 |
| 8 | Octal | 258 |
| 9 | Nonary | 239 |
| 10 | Decimal | 21 |
| 12 | Duodecimal | 1912 |
| 16 | Hexadecimal | 1516 |
| 20 | Vigesimal | 1120 |
| 36 | Base36 | l36 |
| 60 | Sexagesimal | L60 |
Calculation was done in 0.0000181198 seconds
| Square of 21 (n2) | 441 |
| Cube of 21 (n3) | 9261 |
| Square root of 21 | 4.5825756949558 |
| Natural Logarithm (ln) of 21 | 3.0445224377234 |
| Decimal Logarithm (log) of 21 | 1.3222192947339 |
Calculation was done in 0.0000059605 seconds
| Sine of 21 | 0.83665563853606 |
| Cosecant of 21 | 1.1952348779359 |
| Cosine of 21 | -0.54772926022427 |
| Secant of 21 | -1.825719516227 |
| Tangent of 21 | -1.5274985276366 |
| Cotangent of 21 | -0.65466511548606 |
Calculation was done in 0.0000100136 seconds
Is 21 an Odd Number?
Yes, the number 21 is an odd number.
Total number of all odd numbers from 1 to 21 is
11Sum of all the odd numbers from 1 to 21 are
121The sum of all odd numbers is a perfect square: 121 = 11
An odd number is any integer (a whole number) that cannot be divided by 2 evenly. Odd numbers are the opposite of even numbers.Previous odd number is
19
Calculation was done in 0.0000069141 seconds
| The spelling of 21 in words is "twenty-one", meaning that: |
| 21 is an aban number (a number without the letter a) |
| 21 is not an eban number (as it contains the letter e) |
| 21 is an iban number (a number without the letter i) |
| 21 is not an oban number (as it contains the letter o) |
| 21 is not a tban number (as it contains the letter t) |
| 21 is an uban number (a number without the letter u) |
Calculation was done in 0.0000030994 seconds
| Bengali numerals | ২১ |
| Eastern Arabic numerals | ٢١ |
| Hieroglyphs numeralsused in Ancient Egypt | 𓎇𓏺 |
| Khmer numerals | ២១ |
| Japanese numerals | 二十一 |
| Roman numerals | XXI |
| Thai numerals | ๒๑ |
Calculation was done in 0.0000979900 seconds
| Arabic | واحد و عشرون |
| Croatian | dvadeset i jedan |
| Czech | dvacet jeden |
| Danish | en og tyve |
| Dutch | éénentwintig |
| Estonian | blaeve vɔ ɖekɛ |
| Faroese | tjúgoein |
| Filipino | dalawáng pû’t isá |
| Finnish | kaksikymmentäyksi |
| French | vingt et un |
| Greek | είκοσι ένα |
| German | einundzwanzig |
| Hebrew | עשרים ואחת |
| Hindi | इक्कीस |
| Hungarian | huszonegy |
| Icelandic | tuttugu og einn |
| Indonesian | dua puluh satu |
| Italian | ventuno |
| Japanese | 二十一 |
| Korean | 이십일 |
| Latvian | divdesmit viens |
| Lithuanian | dvidešimt vienas |
| Norwegian | tjueén |
| Persian | بیست و یک |
| Polish | dwadzieścia jeden |
| Portuguese | vinte e um |
| Romanian | douăzeci şi unu |
| Russian | двадцать один |
| Serbian | двадесет и један |
| Slovak | dvadsaťjeden |
| Slovene | dvaset ena |
| Spanish | veintiuno |
| Swahili | ishirini na moja |
| Swedish | tjugoen |
| Thai | ยี่สิบเอ็ด |
| Turkish | yirmi bir |
| Ukrainian | двадцять один |
| Vietnamese | hai mươi mốt |
Calculation was done in 0.0147879124 seconds
| Number 21 reversed | 12 |
| ASCII Code | 21 | |
| Unicode Character | U+0015 | |
| Unix Timestamp | Thu, 01 Jan 1970 00:00:21 +0000 |
Calculation was done in 0.0000309944 seconds
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