Template:HAZMAT Class 6 Packing Groups

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

Selected numbers

• 20000 – round number; also in the title of Jules Verne's novel 20,000 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
• 20540 – square pyramidal number
• 20569 – tetranacci number
• 20736 - 12^4, 10000₁₂
• 20903 – first prime of form 120k+23 that is not a full reptend prime
• 21147 – Bell number
• 21181 – one of six remaining Seventeen or Bust numbers in the Sierpinski problem
• 21856 – octahedral number
• 21978 - reverses when multiplied by 4
• 22050 – pentagonal pyramidal number
• 22140 – square pyramidal number
• 22222 – Kaprekar number
• 22447 – cuban prime
• 22527 – Woodall number
• 22699 – one of six remaining Seventeen or Bust numbers in the Sierpinski problem
• 23401 – Leyland number
• 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
• 24571 – cuban prime
• 24601 – Jean Valjean's prisoner number in Les Miserables
• 24631 – Wedderburn-Etherington number
• 24737 – one of six 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
• 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 – $13^4=169^2=119^2+120^2$, number that is simultaneously a square number and a centered square number
• 28595 – octahedral number
• 28657 – Fibonacci number, Markov number
• 29241 – sum of the cubes of the first 18 positive integers
• 29341 – Carmichael number
• 29370 – square pyramidal number