Untouchable number

Rarity: Common

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At a glance

Class

Notion

Domain

Science and technology

In collections

Nobody has pulled it yet.

What Wikipedia says

In mathematics, an untouchable number is a positive integer that cannot be expressed as the sum of all the proper divisors of any positive integer. That is, these numbers are not in the image of the aliquot sum function.

Excerpt from the Wikipedia article “Untouchable number”, under the CC BY-SA 4.0 license. Read the article on Wikipedia