20990

← 20989 20990 20991 →
Cardinaltwenty thousand nine hundred ninety
Ordinal20990th
(twenty thousand nine hundred ninetieth)
Factorization2 × 5 × 2099
Divisors1, 2, 5, 10, 2099, 4198, 10495, 20990, 20990
Greek numeral͵ϡϟ´
Roman numeralXXCMXC, xxcmxc
Binary1010001111111102
Ternary10012101023
Senary2411026
Octal507768
Duodecimal1019212
Hexadecimal51FE16

20990 (twenty thousand nine hundred [and] ninety) is the natural number following 20989 and preceding 20991.

In mathematics

The prime factorization of 20990 is 2 × 5 × 2099, meaning that 20990 is a composite number. It is also a deficient number, since the divisors of 20990 (excluding itself) sum up to 16810, which is less than 20990.

Uninteresting number

As of 2026, 20990 is the smallest uninteresting number, since it doesn't appear in the On-line Encyclopedia of Integer Sequences. In July 2009, 11630 was the smallest uninteresting number for the same reason, until a new integer sequence contained 11630. Being the smallest uninteresting number is considered interesting. 20067 was the previous smallest uninteresting number.

References

  1. 1 2 3 Vanovschi, Vitalii. "Properties of the number 20990". www.numberempire.com. Retrieved 2026-09-17.
  2. ↑ "The Positive Integer 20990". www.positiveintegers.org. Retrieved 2026-10-08.
  3. ↑ "OEIS FUN facts". benwiederhake.github.io. Retrieved 2026-10-07.
  4. 1 2 manman4. "manman4 | OEIS Uninteresting Numbers and Sloane's Gap". manman4.github.io. Retrieved 2026-10-07.{{cite web}}: CS1 maint: numeric names: authors list (link)
  5. ↑ Johnston, Nathaniel (2009-06-12). "11630 is the First Uninteresting Number". Retrieved 2026-10-07.
  6. ↑ Chaitin, Gregory (May 2002). Paradoxes of Randomness (PDF) (Report). CDMTCS Research Report Series. Centre for Discrete Mathematics and Theoretical Computer Science, University of Auckland. CDMTCS-188. Retrieved 2026-09-17.