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220 (number)

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Short description: Natural number
← 219 220 221 →
Cardinaltwo hundred twenty
Ordinal220th
(two hundred twentieth)
Factorization22 × 5 × 11
Greek numeralΣΚ´
Roman numeralCCXX
Binary110111002
Ternary220113
Quaternary31304
Quinary13405
Senary10046
Octal3348
Duodecimal16412
HexadecimalDC16
VigesimalB020
Base 366436

220 (two hundred [and] twenty) is the natural number following 219 and preceding 221.

In mathematics

It is a composite number, with its proper divisors being 1, 2, 4, 5, 10, 11, 20, 22, 44, 55 and 110, making it an amicable number with 284.[1][2] Every number up to 220 may be expressed as a sum of its divisors, making 220 a practical number.[3]

It is the sum of four consecutive primes (47 + 53 + 59 + 61).[4] It is the smallest even number with the property that when represented as a sum of two prime numbers (per Goldbach's conjecture) both of the primes must be greater than or equal to 23.[5] There are exactly 220 different ways of partitioning 64 = 82 into a sum of square numbers.[6]

It is a tetrahedral number, the sum of the first ten triangular numbers,[7] and a dodecahedral number.[8] If all of the diagonals of a regular decagon are drawn, the resulting figure will have exactly 220 regions.[9]

It is the sum of the sums of the divisors of the first 16 positive integers.[10]

Integers between 221 and 229

221

Main article: 221 (number)

222

Main article: 222 (number)

223

Main article: 223 (number)

224

Main article: 224 (number)

225

Main article: 225 (number)

226

Main article: 226 (number)

227

Main article: 227 (number)

228

Main article: 228 (number)

229

Main article: 229 (number)

Notes

  1. ↑ Bryan Bunch, The Kingdom of Infinite Number. New York: W. H. Freeman & Company (2000): 167
  2. ↑ Higgins, Peter (2008). Number Story: From Counting to Cryptography. New York: Copernicus. p. 61. ISBN 978-1-84800-000-1. https://archive.org/details/numberstoryfromc00higg_612. 
  3. ↑ Sloane, N. J. A., ed. "Sequence A005153 (Practical numbers)". OEIS Foundation. https://oeis.org/A005153. 
  4. ↑ Sloane, N. J. A., ed. "Sequence A034963 (Sums of four consecutive primes)". OEIS Foundation. https://oeis.org/A034963. 
  5. ↑ Sloane, N. J. A., ed. "Sequence A025018 (Numbers n such that least prime in Goldbach partition of n increases)". OEIS Foundation. https://oeis.org/A025018. 
  6. ↑ Sloane, N. J. A., ed. "Sequence A037444 (Number of partitions of n^2 into squares)". OEIS Foundation. https://oeis.org/A037444. 
  7. ↑ Sloane, N. J. A., ed. "Sequence A000292 (Tetrahedral (or triangular pyramidal) numbers)". OEIS Foundation. https://oeis.org/A000292. 
  8. ↑ Sloane, N. J. A., ed. "Sequence A006566 (Dodecahedral numbers)". OEIS Foundation. https://oeis.org/A006566. 
  9. ↑ Sloane, N. J. A., ed. "Sequence A007678 (Number of regions in regular n-gon with all diagonals drawn)". OEIS Foundation. https://oeis.org/A007678. 
  10. ↑ Sloane, N. J. A., ed. "Sequence A024916 (sum_{k=1..n} sigma(k) where sigma(n) = sum of divisors of n)". OEIS Foundation. https://oeis.org/A024916. 

References

  • Wells, D. (1987). The Penguin Dictionary of Curious and Interesting Numbers (pp. 145 – 147). London: Penguin Group.



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