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38 (number)

From Wikipedia - Reading time: 6 min
← 37 38 39 →
Cardinalthirty-eight
Ordinal38th
(thirty-eighth)
Factorization2 × 19
Divisors1, 2, 19, 38
Greek numeralΛΗ´
Roman numeralXXXVIII
Binary1001102
Ternary11023
Senary1026
Octal468
Duodecimal3212
Hexadecimal2616

38 (thirty-eight) is the natural number following 37 and preceding 39.

In mathematics

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  • specifically, the 11th discrete Semiprime,[1] it being the 7th of the form (2.q).
  • the first member of the third cluster of two discrete semiprimes 38, 39 the next such cluster is 57, 58.
  • with an aliquot sum of 22 in an aliquot sequence of five composite numbers (38,22,14,10,8,7,1,0) to the Prime in the 7-aliquot tree. 38 is the first semiprime within a chain of 4 semiprimes in its aliquot sequence (38,22,14,10). The next semiprime with a four semiprime chain is 166.
  • 38! − 1 yields 523022617466601111760007224100074291199999999 which is the 16th factorial prime.[2]
  • There is no answer to the equation φ(x) = 38, making 38 a nontotient.[3]
  • 38 is the sum of the squares of the first three primes.
  • 37 and 38 are the first pair of consecutive positive integers not divisible by any of their digits.
  • 38 is the largest even number which cannot be written as the sum of two odd composite numbers.
  • The sum of each row of the only non-trivial (order 3) magic hexagon is 38.[4]

In science

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Astronomy

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In other fields

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Ishihara test: Most people will see the number 38, but people with red-green color blindness might see 88 instead.

Thirty-eight is also:

See also

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References

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  1. ^ Sloane, N. J. A. (ed.). "Sequence A001358". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation.
  2. ^ Sloane, N. J. A. (ed.). "Sequence A002982 (Numbers n such that n! - 1 is prime)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-05-31.
  3. ^ (sequence A005277 in the OEIS)
  4. ^ Higgins, Peter (2008). Number Story: From Counting to Cryptography. New York: Copernicus. p. 53. ISBN 978-1-84800-000-1.
  5. ^ Fry, Michael (5 August 2013). "National Geographic, Korea, and the 38th Parallel". National Geographic. Archived from the original on February 25, 2021. Retrieved 15 May 2021.
  6. ^ Fluck, Daniel (23 March 2010). "Color Blindness Tests". Colblinder. Retrieved 30 November 2022.
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