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"20k" redirects here. For the type of foot race, see
20K run .
Natural number
20,000 (twenty thousand ) is the
natural number that comes after 19,999 and before 20,001.
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
21000 to 21999
22000 to 22999
23000 to 23999
23000 = number of primes
≤
2
18
{\displaystyle \leq 2^{18}}
.
[15]
23401 = Leyland number:
[4] 65 + 56
23409 = 1532 , sum of the cubes of the first 17 positive integers
23497 = cuban prime
[13]
23821 = square pyramidal number
[5]
23833 =
Padovan prime
23969 = octahedral number
[11]
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
[17]
25117 = cuban prime
[13]
25200 = highly composite number, smallest number with exactly 90 factors
[2]
25205 = largest number whose
factorial is less than 10100000
25482 = number of 21-bead necklaces (turning over is allowed) where complements are equivalent
[20]
25585 = square pyramidal number
[5]
25724 = Fine number
[21]
25920 = smallest number with exactly 70 factors
26000 to 26999
26015 = number of partitions of 38
[22]
26214 = octahedral number
[11]
26227 = cuban prime
[13]
26272 = number of 20-bead binary necklaces with beads of 2 colors where the colors may be swapped but turning over is not allowed
[23]
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
27405 =
heptagonal number ,
[24] hexadecagonal number,
[25] 48-gonal number, 80-gonal number, smallest integer that is polygonal in exactly 10 ways.
[26]
27434 = square pyramidal number
[5]
27559 = Zeisel number
[17]
27594 = number of primitive polynomials of degree 19 over GF(2)
[16]
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
[27]
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
[11]
28657 =
Fibonacci prime ,
[28] Markov prime
[29]
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
[30]
29370 = square pyramidal number
[5]
29527 = Friedman prime
29531 = Friedman prime
29601 = number of planar partitions of 18
[31]
29791 = 313
Primes
There are 983
prime numbers between 20000 and 30000.
References
^
Sloane, N. J. A. (ed.).
"Sequence A005893 (Number of points on surface of tetrahedron)" . The
On-Line Encyclopedia of Integer Sequences . OEIS Foundation.
^
a
b
c
Sloane, N. J. A. (ed.).
"Sequence A002182 (Highly composite numbers)" . The
On-Line Encyclopedia of Integer Sequences . OEIS Foundation.
^
a
b
c
d
Sloane, N. J. A. (ed.).
"Sequence A002411 (Pentagonal pyramidal numbers)" . The
On-Line Encyclopedia of Integer Sequences . OEIS Foundation.
^
a
b
Sloane, N. J. A. (ed.).
"Sequence A076980 (Leyland numbers)" . The
On-Line Encyclopedia of Integer Sequences . OEIS Foundation.
^
a
b
c
d
e
f
Sloane, N. J. A. (ed.).
"Sequence A000330 (Square pyramidal numbers)" . The
On-Line Encyclopedia of Integer Sequences . OEIS Foundation.
^
Sloane, N. J. A. (ed.).
"Sequence A000078 (Tetranacci numbers)" . The
On-Line Encyclopedia of Integer Sequences . OEIS Foundation.
^
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 .
^
Sloane, N. J. A. (ed.).
"Sequence A000110 (Bell or exponential numbers)" . The
On-Line Encyclopedia of Integer Sequences . OEIS Foundation.
^
Sloane, N. J. A. (ed.).
"Sequence A000014 (Number of series-reduced trees with n nodes)" . The
On-Line Encyclopedia of Integer Sequences . OEIS Foundation.
^
Sloane, N. J. A. (ed.).
"Sequence A000041 (a(n) is the number of partitions of n (the partition numbers))" . The
On-Line Encyclopedia of Integer Sequences . OEIS Foundation.
^
a
b
c
d
Sloane, N. J. A. (ed.).
"Sequence A005900 (Octahedral numbers)" . The
On-Line Encyclopedia of Integer Sequences . OEIS Foundation.
^
Sloane, N. J. A. (ed.).
"Sequence A006886 (Kaprekar numbers)" . The
On-Line Encyclopedia of Integer Sequences . OEIS Foundation.
^
a
b
c
d
e
Sloane, N. J. A. (ed.).
"Sequence A002407 (Cuban primes)" . The
On-Line Encyclopedia of Integer Sequences . OEIS Foundation.
^
Sloane, N. J. A. (ed.).
"Sequence A003261 (Woodall numbers)" . The
On-Line Encyclopedia of Integer Sequences . OEIS Foundation.
^
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 .
^
a
b
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.
^
a
b
c
Sloane, N. J. A. (ed.).
"Sequence A051015 (Zeisel numbers)" . The
On-Line Encyclopedia of Integer Sequences . OEIS Foundation.
^
Sloane, N. J. A. (ed.).
"Sequence A001190 (Wedderburn-Etherington numbers)" . The
On-Line Encyclopedia of Integer Sequences . OEIS Foundation.
^
Sloane, N. J. A. (ed.).
"Sequence A000060 (Number of signed trees with n nodes)" . The
On-Line Encyclopedia of Integer Sequences . OEIS Foundation.
^
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.
^
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 .
^
Sloane, N. J. A. (ed.).
"Sequence A000041 (a(n) is the number of partitions of n (the partition numbers))" . The
On-Line Encyclopedia of Integer Sequences . OEIS Foundation.
^
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.
^
Sloane, N. J. A. (ed.).
"Sequence A000566 (Heptagonal numbers)" . The
On-Line Encyclopedia of Integer Sequences . OEIS Foundation.
^
Sloane, N. J. A. (ed.).
"Sequence A051868 (Hexadecagonal numbers)" . The
On-Line Encyclopedia of Integer Sequences . OEIS Foundation.
^
Sloane, N. J. A. (ed.).
"Sequence A063778 (a(n) = the least integer that is polygonal in exactly n ways.)" . The
On-Line Encyclopedia of Integer Sequences . OEIS Foundation.
^
"Sloane's A001599 : Harmonic or Ore numbers" . The On-Line Encyclopedia of Integer Sequences . OEIS Foundation. Retrieved 2016-06-15 .
^
"Sloane's A000045 : Fibonacci numbers" . The On-Line Encyclopedia of Integer Sequences . OEIS Foundation. Retrieved 2016-06-15 .
^
"Sloane's A002559 : Markoff (or Markov) numbers" . The On-Line Encyclopedia of Integer Sequences . OEIS Foundation. Retrieved 2016-06-15 .
^
"Sloane's A002997 : Carmichael numbers" . The On-Line Encyclopedia of Integer Sequences . OEIS Foundation. Retrieved 2016-06-15 .
^
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.
100,000
1,000,000
10,000,000
100,000,000
1,000,000,000