# 20,000

 ← 19999 20000 20001 →
Cardinaltwenty thousand
Ordinal20000th
(twenty thousandth)
Factorization25 × 54
Greek numeral${\displaystyle {\stackrel {\beta }{\mathrm {M} }}}$
Roman numeralXX
Binary1001110001000002
Ternary10001022023
Quaternary103202004
Quinary11200005
Senary2323326
Octal470408
DuodecimalB6A812
Vigesimal2A0020
Base 36FFK36

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

### 23000 to 23999

• 23401 – Leyland number:[3] 65 + 56
• 23409 – sum of the cubes of the first 17 positive integers
• 23497 – cuban prime[9]
• 23821 – square pyramidal number[4]
• 23969 – octahedral number[7]
• 23976 – pentagonal pyramidal number[2]

### 25000 to 25999

• 25011 – the first composite number that in base 10 remains composite after any insertion of a digit
• 25085 – Zeisel number[11]
• 25117 – cuban prime[9]
• 25200 – highly composite number[1]
• 25205 – largest number whose factorial is less than 10100000
• 25585 – square pyramidal number[4]

### 26000 to 26999

• 26214 – octahedral number[7]
• 26227 – cuban prime[9]
• 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 to 27999

• 27000 – 303
• 27434 – square pyramidal number[4]
• 27559 – Zeisel number[11]
• 27648 – 11 × 22 × 33 × 44
• 27720 – highly composite number;[1] smallest number divisible by the numbers 1 to 12 (there is no smaller number divisible by the numbers 1 to 11)
• 27846harmonic divisor number[13]

### 29000 to 29999

• 29241 – sum of the cubes of the first 18 positive integers
• 29341Carmichael number[16]
• 29370 – square pyramidal number[4]
• 29791 – 313

## References

1. ^ a b c "Sloane's A002182 : Highly composite numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-15.
2. ^ a b c d "Sloane's A002411 : Pentagonal pyramidal numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-15.
3. ^ a b "Sloane's A076980 : Leyland numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-15.
4. "Sloane's A000330 : Square pyramidal numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-15.
5. ^ "Sloane's A000078 : Tetranacci numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-15.
6. ^ "Sloane's A000110 : Bell or exponential numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-15.
7. ^ a b c d "Sloane's A005900 : Octahedral numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-15.
8. ^ "Sloane's A006886 : Kaprekar numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-15.
9. "Sloane's A002407 : Cuban primes". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-15.
10. ^ "Sloane's A003261 : Woodall numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-15.
11. ^ a b c "Sloane's A051015 : Zeisel numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-15.
12. ^ "Sloane's A001190 : Wedderburn-Etherington numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-15.
13. ^ "Sloane's A001599 : Harmonic or Ore numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-15.
14. ^ "Sloane's A000045 : Fibonacci numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-15.
15. ^ "Sloane's A002559 : Markoff (or Markov) numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-15.
16. ^ "Sloane's A002997 : Carmichael numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-15.