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21

natural number
Intangible positive_integer Q712477

Facts

11 properties
Instance of
positive integer, deficient number, triangular number, odd number, centered pentachoric number, octagonal number, highly touchable number, Fibonacci number, composite number, harshad number[2][3][4][5][6][7][8][9][10]
Follows
20[11]
Followed by
22[12]
Code
௨௰௧, ௨௧, XXI, 𒎙𒐕, 10101, 25, 19, 15, 210, 111, 41, 33, 30, 23, 21, 1A, 18, 17, 16, 14, 13, 12, 11, 10, ΚΑʹ, ൨൧, ൨൰൧[16][17][18][19][20][21][22][23][24][25][26][27][28][29]
Different from
21[15]
Maintained by WikiProject
WikiProject Mathematics[32]
Name in hiero markup
V20-V20-Z1[34]
Number of decimal digits
+2[33]
Numeric value
+21[14]
Prime factor
3, 7[30][31]
Unicode character
㉑[13]
🏷️ Also known as
en 21 en 1*21 en twenty-one en twenty one en the number 21 en 21*1 en ㉑ ar ٢١ (عدد) ar واحد وعشرون cs dvacet jedna cs dvacet jednička cs dvacet jeden cs jednadvacet cs jednadvacítka cs XXI da enogtyve de einundzwanzig de Einundzwanzig el ΚΑʹ el είκοσι ένα
🔖 Identifiers · 10
Image (Wikimedia Commons)
Zlin skyscraper 01.jpg ↗
BabelNet ID
00000081n
Concepticon concept set ID
1734
FactGrid item ID
dual wield
Factordb ID
21
Fandom article ID
googology:21
KIT Linked Open Numbers ID
21
OmegaWiki Defined Meaning
7046
UMLS CUI
C3715213
WikiKids ID
21_(getal)

Report an error or request removal Lineage (PROV-JSON)

🔗 Connections
Instance of 7
Fibonacci number, composite number, triangular number, deficient number, odd number, harshad number, octagonal number
Different from 1
21
FactGrid item ID 1
dual wield
Followed by 1
22
Followed by (predecessor) 1
22
Follows 1
20
Maintained by WikiProject 1
WikiProject Mathematics
Preceded by (successor) 1
20
Prime factor 1
3
← Calculated from 1
21:9
← FactGrid item ID 1
Zalissia
← Set cardinality 1
Karp's 21 NP-complete problems
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Summary

21 is a positive integer[1].

References

Programmatic citations — every numbered marker resolves to a verifiable graph row below.

Direct Wikidata claims

  1. [2] ↑ . wikidata.org.
  2. [3] ↑ . wikidata.org.
  3. [4] ↑ . wikidata.org.
  4. [5] ↑ . wikidata.org.
  5. [6] ↑ . wikidata.org.
  6. [7] ↑ . wikidata.org.
  7. [8] ↑ . wikidata.org.
  8. [9] ↑ . wikidata.org.
  9. [10] ↑ . wikidata.org.
  10. [11] ↑ . wikidata.org.
  11. [12] ↑ . wikidata.org.
  12. [13] ↑ . wikidata.org.
  13. [14] ↑ . wikidata.org.
  14. [15] ↑ . wikidata.org.
  15. [16] ↑ . wikidata.org.
  16. [17] ↑ . wikidata.org.
  17. [18] ↑ . wikidata.org.
  18. [19] ↑ . wikidata.org.
  19. [20] ↑ . wikidata.org.
  20. [21] ↑ . wikidata.org.
  21. [22] ↑ . wikidata.org.
  22. [23] ↑ . wikidata.org.
  23. [24] ↑ . wikidata.org.
  24. [25] ↑ . wikidata.org.
  25. [26] ↑ . wikidata.org.
  26. [27] ↑ . wikidata.org.
  27. [28] ↑ . wikidata.org.
  28. [29] ↑ . wikidata.org.
  29. [30] ↑ . wikidata.org.
  30. [31] ↑ . wikidata.org.
  31. [32] ↑ . wikidata.org.
  32. [33] ↑ . wikidata.org.
  33. [34] ↑ . wikidata.org.

Class ancestry

  1. [1] ↑ . Wikidata. wikidata.org.

📑 Cite this page

Use these citations when quoting this entity in research, articles, AI prompts, or wherever provenance matters. We aggregate Wikidata + Wikipedia + authoritative open-data sources; the stitched, scored, cross-referenced view is what 4ort.xyz contributes.

APA 4ort.xyz Knowledge Graph. (2026). 21. Retrieved November 5, 2026, from https://4ort.xyz/entity/21-q712477
MLA “21.” 4ort.xyz Knowledge Graph, 4ort.xyz, 5 Nov. 2026, https://4ort.xyz/entity/21-q712477.
BibTeX @misc{4ortxyz_21-q712477_2026, author = {{4ort.xyz Knowledge Graph}}, title = {{21}}, year = {2026}, url = {https://4ort.xyz/entity/21-q712477}, note = {Accessed: 2026-11-05}}
LLM prompt According to 4ort.xyz Knowledge Graph (aggregator of Wikidata, Wikipedia, and authoritative open-data sources): 21 — https://4ort.xyz/entity/21-q712477 (retrieved 2026-11-05)

Canonical URL: https://4ort.xyz/entity/21-q712477 · Last refreshed:

Edit History

Rolling log of changes to this entity's Wikidata record. Values shown reflect the current state of each edited property — follow the history link to see the precise diff for any edit.

  1. 9w ago · Mahir256 · 2026-08-31 view diff on Wikidata ↗
    UMLS CUI → C3715213
    "/* wbeditentity-update:0| */ QuickStatements 3.0 [[:toollabs:qs-dev/batch/50960|batch #50960]]"
  2. 26w ago · KrBot bot · 2026-05-06 view diff on Wikidata ↗
    Instance of → positive integer, deficient number, triangular number +7
    "/* wbsetclaimvalue:1| */ Instance of: positive integer, разрешение перенаправления / resolving redirect positive integer → positive integer ([[:toollabs:editgroups/b/KrBotResolvingRedirect/Q28920044_Q"
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