20,000

20,000 (twenty thousand) is the natural number that comes after 19,999 and before 20,001.

19999 20000 20001
Cardinaltwenty thousand
Ordinal20000th
(twenty thousandth)
Factorization25 × 54
Greek numeral
Roman numeralXX
Binary1001110001000002
Ternary10001022023
Senary2323326
Octal470408
DuodecimalB6A812
Hexadecimal4E2016

20,000 is a round number, and is also in the title of Jules Verne's novel Twenty Thousand Leagues Under the Sea.

Selected numbers in the range 20001–29999

20001 to 20999

  • 20002 = number of surface-points of a tetrahedron with edge-length 100[1]
  • 20067 = The smallest number with no entry in the Online Encyclopedia of Integer Sequences (OEIS)Bischoff, Manon (March 3, 2023). "The Most Boring Number in the World Is ..." Scientific American. Springer Nature.
  • 20100 = sum of the first 200 natural numbers (hence a triangular number)
  • 20160 = highly composite number;[2] the smallest order belonging to two non-isomorphic simple groups: the alternating group A8 and the Chevalley group A2(4)
  • 20161 = the largest integer that cannot be expressed as a sum of two abundant numbers
  • 20230 = pentagonal pyramidal number[3]
  • 20412 = Leyland number:[4] 93 + 39
  • 20540 = square pyramidal number[5]
  • 20569 = tetranacci number[6]
  • 20593 = unique prime in base 12
  • 20597 = k such that the sum of the squares of the first k primes is divisible by k.[7]
  • 20736 = 1442 = 124, 1000012, palindromic in base 15 (622615)
  • 20793 = little Schroeder number
  • 20871 = The number of weeks in exactly 400 years in the Gregorian calendar
  • 20903 = first prime of form 120k + 23 that is not a full reptend prime

21000 to 21999

22000 to 22999

23000 to 23999

  • 23000 = number of primes .[14]
  • 23401 = Leyland number:[4] 65 + 56
  • 23409 = 1532, sum of the cubes of the first 17 positive integers
  • 23497 = cuban prime[12]
  • 23821 = square pyramidal number[5]
  • 23833 = Padovan prime
  • 23969 = octahedral number[10]
  • 23976 = pentagonal pyramidal number[3]

24000 to 24999

25000 to 25999

  • 25011 = the smallest composite number, ending in 1, 3, 7, or 9, that in base 10 remains composite after any insertion of a digit
  • 25085 = Zeisel number[16]
  • 25117 = cuban prime[12]
  • 25200 = highly composite number[2]
  • 25205 = largest number whose factorial is less than 10100000
  • 25482 = number of 21-bead necklaces (turning over is allowed) where complements are equivalent[18]
  • 25585 = square pyramidal number[5]
  • 25724 = Fine number[19]

26000 to 26999

  • 26214 = octahedral number[10]
  • 26227 = cuban prime[12]
  • 26272 = number of 20-bead binary necklaces with beads of 2 colors where the colors may be swapped but turning over is not allowed[20]
  • 26861 = smallest number for which there are more primes of the form 4k + 1 than of the form 4k + 3 up to the number, against Chebyshev's bias
  • 26896 = 1642, palindromic in base 9: 408049

27000 to 27999

  • 27000 = 303
  • 27434 = square pyramidal number[5]
  • 27559 = Zeisel number[16]
  • 27594 = number of primitive polynomials of degree 19 over GF(2)[21]
  • 27648 = 11 × 22 × 33 × 44
  • 27653 = Friedman prime
  • 27720 = highly composite number;[2] smallest number divisible by the numbers 1 to 12 (there is no smaller number divisible by the numbers 1 to 11 since any number divisible by 4 and 3 must be divisible by 12, since 4×3=12)
  • 27846 = harmonic divisor number[22]
  • 27889 = 1672

28000 to 28999

  • 28158 = pentagonal pyramidal number[3]
  • 28374 = smallest integer to start a run of six consecutive integers with the same number of divisors
  • 28393 = unique prime in base 13
  • 28547 = Friedman prime
  • 28559 = nice Friedman prime
  • 28561 = 1692 = 134 = 1192 + 1202, number that is simultaneously a square number and a centered square number, palindromic in base 12: 1464112
  • 28595 = octahedral number[10]
  • 28657 = Fibonacci prime,[23] Markov prime[24]
  • 28900 = 1702, palindromic in base 13: 1020113

29000 to 29999

  • 29241 = 1712, sum of the cubes of the first 18 positive integers
  • 29341 = Carmichael number[25]
  • 29370 = square pyramidal number[5]
  • 29527 = Friedman prime
  • 29531 = Friedman prime
  • 29601 = number of planar partitions of 18[26]
  • 29791 = 313

Primes

There are 983 prime numbers between 20000 and 30000.

References

  1. Sloane, N. J. A. (ed.). "Sequence A005893 (Number of points on surface of tetrahedron)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation.
  2. "Sloane's A002182 : Highly composite numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-15.
  3. "Sloane's A002411 : Pentagonal pyramidal numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-15.
  4. "Sloane's A076980 : Leyland numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-15.
  5. "Sloane's A000330 : Square pyramidal numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-15.
  6. "Sloane's A000078 : Tetranacci numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-15.
  7. Sloane, N. J. A. (ed.). "Sequence A111441 (Numbers k such that the sum of the squares of the first k primes is divisible by k)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2022-06-02.
  8. "Sloane's A000110 : Bell or exponential numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-15.
  9. Sloane, N. J. A. (ed.). "Sequence A000014 (Number of series-reduced trees with n nodes)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation.
  10. "Sloane's A005900 : Octahedral numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-15.
  11. "Sloane's A006886 : Kaprekar numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-15.
  12. "Sloane's A002407 : Cuban primes". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-15.
  13. "Sloane's A003261 : Woodall numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-15.
  14. Sloane, N. J. A. (ed.). "Sequence A007053 (Number of primes [greater than or equal to] 2^n)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2022-06-02.
  15. Sloane, N. J. A. (ed.). "Sequence A011260 (Number of primitive polynomials of degree n over GF(2))". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation.
  16. "Sloane's A051015 : Zeisel numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-15.
  17. "Sloane's A001190 : Wedderburn-Etherington numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-15.
  18. Sloane, N. J. A. (ed.). "Sequence A000011 (Number of n-bead necklaces (turning over is allowed) where complements are equivalent)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation.
  19. Sloane, N. J. A. (ed.). "Sequence A000957 (Fine's sequence (or Fine numbers): number of relations of valence > 0 on an n-set; also number of ordered rooted trees with n edges having root of even degree)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2022-06-01.
  20. Sloane, N. J. A. (ed.). "Sequence A000013 (Definition (1): Number of n-bead binary necklaces with beads of 2 colors where the colors may be swapped but turning over is not allowed)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation.
  21. Sloane, N. J. A. (ed.). "Sequence A011260 (Number of primitive polynomials of degree n over GF(2))". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation.
  22. "Sloane's A001599 : Harmonic or Ore numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-15.
  23. "Sloane's A000045 : Fibonacci numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-15.
  24. "Sloane's A002559 : Markoff (or Markov) numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-15.
  25. "Sloane's A002997 : Carmichael numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-15.
  26. Sloane, N. J. A. (ed.). "Sequence A000219 (Number of planar partitions (or plane partitions) of n)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation.
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