# Ibn Fallus

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{{Short description|Egyptian mathematician (1194–1252)}}
{{infobox person
| honorific_prefix   = Shams ad-Din
| name               = 
| honorific_suffix   = al-Ḥanafī al-Māridīnī
| other_names        = Ismāʽīl ibn-Fullūs
| birth_name         = Ismāʽīl ibn-Ibrāhīm ibn-Ġāzī ibn-ʽAlī ibn Muhammad
| birth_date         = 1194
| birth_place        = [Mardin](/source/Mardin)
| death_date         = {{Death year and age|1252|1194}}
| occupation         = [Mathematician](/source/Mathematician)
}}
'''Shams ad-Dīn Abû’t-Tāhir Ismāʽīl ibn-Ibrāhīm ibn-Ġāzī ibn-ʽAlī ibn Muhammad al-Ḥanafī al-Māridīnī''' (1194–1252),<ref>Brentjes, Sonja (1988). [https://dergipark.org.tr/tr/download/article-file/693083 "The First Perfect Numbers and Three Types of Amicable Numbers in a Manuscript on Elementary Number Theory by Ibn Fallûs"]. ''Erdem'', <abbr>vol.</abbr> 5, no. 11. pp. 468–469.</ref> often called '''Ismāʽīl ibn-Fullūs''' or '''Ibn Fallus''', was an [Arab Egyptian](/source/Arab_Egyptians) mathematician of the [Islamic Golden Age](/source/Islamic_Golden_Age). Whilst on pilgrimage to [Mecca](/source/Mecca), he tells of an [epitome](/source/epitome) he wrote on [number theory](/source/number_theory) (extant in manuscript), which building on the work of [Nicomachus](/source/Nicomachus), added three new [perfect numbers](/source/Perfect_number) (33,550,336; 8,589,869,056; and 137,438,691,328) to the four already discovered by the Greeks.

His table also included seven other supposed perfect numbers which are now known to be incorrect. [Roshdi Rashed](/source/Roshdi_Rashed) believes the errors emerged from over-reliance on Nicomachus' method.<ref>Rashed, Roshdi (1994). ''The Development of Arabic Mathematics: Between Arithmetic and Algebra''. Dordrecht: Kluwer Academic. pp. 328–329.</ref>

This work did not reach Europe, and these three perfect numbers were only rediscovered there during the [Renaissance](/source/Renaissance), including by [Pietro Cataldi](/source/Pietro_Cataldi).<ref>Scott, Paul. [https://files.eric.ed.gov/fulltext/EJ769973.pdf "Just Perfect, part 2"]. ''The Australian Mathematics Teacher'', vol. 63, no. 2. p. 3.</ref>

== Further reading ==
* Ismāʽīl ibn-Fullūs, [http://resolver.staatsbibliothek-berlin.de/SBB000040F500020000 Iʽdād al-asrār fī asrār al-iʽdād]

== See also ==
* [Regiomontanus](/source/Regiomontanus)
* [Johannes Scheubel](/source/Johannes_Scheubel) 
* [Pietro Cataldi](/source/Pietro_Cataldi)

== References ==
{{Reflist}}

{{Authority control}}

Category:1194 births
Category:Medieval Egyptian mathematicians
Category:1252 deaths

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Adapted from the Wikipedia article [Ibn Fallus](https://en.wikipedia.org/wiki/Ibn_Fallus) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Ibn_Fallus?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.