20,000

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List of numbers Integers ← 0 10k 20k 30k 40k 50k 60k 70k 80k 90k →
Cardinal	twenty thousand
Ordinal	20000th (twenty thousandth)
Factorization	25 × 54
Greek numeral	${\stackrel {\beta }{\mathrm {M} }}$
Roman numeral	XX
Binary	1001110001000002
Ternary	10001022023
Senary	2323326
Octal	470408
Duodecimal	B6A812
Hexadecimal	4E2016

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

Selected numbers in the range 20000–29999

• 20000 – round number; also in the title of Jules Verne's novel Twenty Thousand Leagues Under the Sea
• 20081 – Motorola 68K instruction for no operation (NOP)
• 20100 – sum of the first 200 natural numbers (hence a triangular number)
• 20160 – highly composite number; 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
• 20412 – Leyland number: 9³ + 3⁹
• 20540 – square pyramidal number
• 20569 – tetranacci number
• 20736 – 12⁴, 10000₁₂, palindromic in base 15 (6226₁₅)
• 20903 – first prime of form 120k + 23 that is not a full reptend prime
• 21025 – 145², palindromic in base 12 (10201₁₂)
• 21147 – Bell number
• 21181 – the least of five remaining Seventeen or Bust numbers in the Sierpiński problem
• 21856 – octahedral number
• 21952 – 28³
• 21978 – reverses when multiplied by 4: 4 × 21978 = 87912
• 22050 – pentagonal pyramidal number
• 22140 – square pyramidal number
• 22222 – Kaprekar number: 22222² = 493817284, 4938 + 17284 = 22222
• 22447 – cuban prime
• 22527 – Woodall number: 11 × 2¹¹ − 1
• 22699 – one of five remaining Seventeen or Bust numbers in the Sierpiński problem
• 23401 – Leyland number: 6⁵ + 5⁶
• 23409 – sum of the cubes of the first 17 positive integers
• 23497 – cuban prime
• 23821 – square pyramidal number
• 23969 – octahedral number
• 23976 – pentagonal pyramidal number
• 24211 – Zeisel number
• 24336 – 156², palindromic in base 5: 1234321₅
• 24389 – 29³
• 24571 – cuban prime
• 24601 – Jean Valjean's prisoner number in Les Misérables
• 24631 – Wedderburn-Etherington number
• 24649 – 157², palindromic in base 12: 12321₁₂
• 24737 – one of five remaining Seventeen or Bust numbers in the Sierpinski problem
• 25011 – the first composite number that in base 10 remains composite after any insertion of a digit
• 25085 – Zeisel number
• 25117 – cuban prime
• 25200 – highly composite number
• 25205 – largest number whose factorial is less than 10¹⁰⁰⁰⁰⁰
• 25585 – square pyramidal number
• 26214 – octahedral number
• 26227 – cuban prime
• 26861 – smallest number below which there are more primes of the form 4k + 1 than of the form 4k + 3, against Chebyshev's bias
• 26896 – 164², palindromic in base 9: 40804₉
• 27000 – 30³
• 27434 – square pyramidal number
• 27559 – Zeisel number
• 27648 – 1¹ × 2² × 3³ × 4⁴
• 27720 – highly composite number; smallest number divisible by the numbers 1 to 12 (there is no smaller number divisible by the numbers 1 to 11)
• 27846 – harmonic divisor number
• 28158 – pentagonal pyramidal number
• 28374 – smallest integer to start a run of six consecutive integers with the same number of divisors
• 28561 – 13⁴, 119² + 120², number that is simultaneously a square number and a centered square number, palindromic in base 12: 14641₁₂
• 28595 – octahedral number
• 28657 – Fibonacci number, Markov number
• 28900 – 170², palindromic in base 13: 10201₁₃
• 29241 – sum of the cubes of the first 18 positive integers
• 29341 – Carmichael number
• 29370 – square pyramidal number
• 29791 – 31³