# 40

> natural number

**Wikidata**: [Q42317](https://www.wikidata.org/wiki/Q42317)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/40_(number))  
**Source**: https://4ort.xyz/entity/40-q42317


## References

1. On Zumkeller Numbers
2. [On-Line Encyclopedia of Integer Sequences](https://oeis.org/A005101)
3. [Source](https://github.com/JohnMarkOckerbloom/ftl/blob/master/data/wikimap)
4. [Source](https://lingualibre.fr/wiki/Q287781)
5. [Source](https://islamansiklopedisi.org.tr/kirk)
6. National Library of Israel