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Hartogs number

given a set, the least ordinal such that there is no injection from the ordinal into the set
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Hartogs number

Summary

Hartogs number ranks in the top 2% of general entities by monthly Wikipedia readership (14 views/month).[1]

Key Facts

  • Friedrich Hartogs is named after Hartogs number[2].
  • Hartogs number's subclass of is recorded as ordinal number[3].
  • Hartogs number's Freebase ID is recorded as /m/08h94y[4].
  • Hartogs number's nLab ID is recorded as Hartogs number[5].
  • Hartogs number's Microsoft Academic ID is recorded as 202634877[6].
  • Hartogs number's ProofWiki ID is recorded as Definition:Hartogs_Number[7].
  • Hartogs number's Metamath statement ID is recorded as df-har[8].

Why It Matters

Hartogs number ranks in the top 2% of general entities by monthly Wikipedia readership (14 views/month).[1] It has Wikipedia articles in 10 language editions, a strong signal of global cultural recognition.[9] It is known by 6 alternative names across languages and contexts.[10]

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] ↑ . Freebase Data Dumps. wikidata.org.
  4. [5] ↑ . wikidata.org.
  5. [6] ↑ . wikidata.org.
  6. [7] ↑ . wikidata.org.
  7. [8] ↑ . wikidata.org.

Aggregate / graph-position facts

  1. [1] ↑ . Wikimedia Foundation. dumps.wikimedia.org.
  2. [9] ↑ . Wikidata sitelinks. wikidata.org.
  3. [10] ↑ . Wikidata aliases. 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). Hartogs number. Retrieved April 10, 2026, from https://4ort.xyz/entity/hartogs-number
MLA “Hartogs number.” 4ort.xyz Knowledge Graph, 4ort.xyz, 10 Apr. 2026, https://4ort.xyz/entity/hartogs-number.
BibTeX @misc{4ortxyz_hartogs-number_2026, author = {{4ort.xyz Knowledge Graph}}, title = {{Hartogs number}}, year = {2026}, url = {https://4ort.xyz/entity/hartogs-number}, note = {Accessed: 2026-04-10}}
LLM prompt According to 4ort.xyz Knowledge Graph (aggregator of Wikidata, Wikipedia, and authoritative open-data sources): Hartogs number — https://4ort.xyz/entity/hartogs-number (retrieved 2026-04-10)

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