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{{Short description|Integer}} |
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| number = 215 |
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| cardinal = two hundred [and] fifteen |
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| number = 215 |
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| numeral = |
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| factorization = <math>5 \cdot 43</math> |
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'''215 (two hundred and fifteen)''' is the [[natural number]] following [[214 (number)|214]] and preceding [[216 (number)|216]]. |
'''215 (two hundred [and] fifteen)''' is the [[natural number]] following [[214 (number)|214]] and preceding [[216 (number)|216]]. |
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==In mathematics== |
==In mathematics== |
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*215 is a [[composite number]] and a [[semiprime]]. |
*215 is a [[composite number]] and a [[semiprime]] (<math>=5\times43</math>). |
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*<math>215 = (3!)^3 - 1</math> |
*<math>215 = (3!)^3 - 1</math>. |
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*215 is the second smallest integer (after 5) such that <math>n^2-17</math> is twice a square: <math>215^2-17 = 2 \times 152^2 |
*215 is the second smallest integer (after 5) such that <math>n^2-17</math> is twice a square: <math>215^2-17 = 2 \times 152^2</math>.<ref>{{OEIS|A144796}}</ref> |
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*There are 215 sequences of four integers, counting re-arrangements as distinct, such that the sum of their reciprocals is 1.<ref>{{OEIS|A002967}}</ref> These are |
*215 is a vertically symmetric number on a calculator display {{OEIS|id=A053701}}. |
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*There are 215 sequences of four integers, counting re-arrangements as distinct, such that the sum of their reciprocals is 1.<ref>{{OEIS|A002967}}</ref> These are: |
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**24 arrangements of (2,3,7,42), (2,3,8,24), (2,3,9,18), (2,3,10,15), (2,4,5,20) and (2,4,6,12). |
**24 arrangements of (2,3,7,42), (2,3,8,24), (2,3,9,18), (2,3,10,15), (2,4,5,20) and (2,4,6,12). |
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**12 arrangements of (3,3,4,12), (3,4,4,6), (2,3,12,12), (2,4,8,8) and (2,5,5,10). |
**12 arrangements of (3,3,4,12), (3,4,4,6), (2,3,12,12), (2,4,8,8) and (2,5,5,10). |
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==In other fields== |
==In other fields== |
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*[[215 Oenone]] is a [[Asteroid belt| |
*[[215 Oenone]] is a [[Asteroid belt|main belt]] [[asteroid]]. |
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*E215 is the [[E number]] of [[Sodium ethyl para-hydroxybenzoate]]. |
*E215 is the [[E number]] of [[Sodium ethyl para-hydroxybenzoate]]. |
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*There are several [[List of highways numbered 215|highways numbered 215]]. |
*There are several [[List of highways numbered 215|highways numbered 215]]. |
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*The [[Dewey Decimal Classification]] for [[Science and religion]]. |
*The [[Dewey Decimal Classification]] for [[Science and religion]]. |
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*The year AD '''[[215]]''' or [[215 BC]] |
*The year AD '''[[215]]''' or [[215 BC]] |
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*215 is often used as slang for [[marijuana]], from [[California Proposition 215 (1996)|California Proposition 215]], legalizing it for [[medical marijuana|medical use]]. |
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*The first [[area code]] of metropolitan [[Philadelphia, Pennsylvania]] |
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==References== |
==References== |
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{{reflist}} |
{{reflist}} |
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{{Integers|2}} |
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[[Category:Integers]] |
[[Category:Integers]] |
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[[ca:Nombre 210#Nombres del 211 al 219]] |
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[[fr:215 (nombre)]] |
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[[ko:215]] |
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[[ht:215 (nonm)]] |
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[[hu:215 (szám)]] |
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[[mk:215 (број)]] |
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[[ja:215]] |
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[[ru:215 (число)]] |
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[[uk:215 (число)]] |
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[[zh:215]] |
Latest revision as of 17:32, 22 April 2024
This article needs additional citations for verification. (August 2012) |
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Cardinal | two hundred fifteen | |||
Ordinal | 215th (two hundred fifteenth) | |||
Factorization | 5 × 43 | |||
Divisors | 5, 43 | |||
Greek numeral | ΣΙΕ´ | |||
Roman numeral | CCXV | |||
Binary | 110101112 | |||
Ternary | 212223 | |||
Senary | 5556 | |||
Octal | 3278 | |||
Duodecimal | 15B12 | |||
Hexadecimal | D716 |
215 (two hundred [and] fifteen) is the natural number following 214 and preceding 216.
In mathematics
[edit]- 215 is a composite number and a semiprime ().
- .
- 215 is the second smallest integer (after 5) such that is twice a square: .[1]
- 215 is a vertically symmetric number on a calculator display (sequence A053701 in the OEIS).
- There are 215 sequences of four integers, counting re-arrangements as distinct, such that the sum of their reciprocals is 1.[2] These are:
- 24 arrangements of (2,3,7,42), (2,3,8,24), (2,3,9,18), (2,3,10,15), (2,4,5,20) and (2,4,6,12).
- 12 arrangements of (3,3,4,12), (3,4,4,6), (2,3,12,12), (2,4,8,8) and (2,5,5,10).
- 6 arrangements of (3,3,6,6).
- 4 arrangements of (2,6,6,6).
- 1 arrangement of (4,4,4,4).
In other fields
[edit]- 215 Oenone is a main belt asteroid.
- E215 is the E number of Sodium ethyl para-hydroxybenzoate.
- There are several highways numbered 215.
215 is also:
- The Dewey Decimal Classification for Science and religion.
- The year AD 215 or 215 BC
- 215 is often used as slang for marijuana, from California Proposition 215, legalizing it for medical use.
- The first area code of metropolitan Philadelphia, Pennsylvania