English

Porous Numbers

General Mathematics 2021-04-07 v1

Abstract

The concept of porous numbers is presented. A number kk which is not a multiple of 10 is called {\it porous} if every number mm with sum of digits = kk and kk a divisor of both mm and digit reversal of mm has a zero in its digits. It is proved that 11, 37, 74, 101 and 121 are the only porous numbers smaller than 1000.

Keywords

Cite

@article{arxiv.2104.02482,
  title  = {Porous Numbers},
  author = {Rüdiger Jehn},
  journal= {arXiv preprint arXiv:2104.02482},
  year   = {2021}
}

Comments

9 pages

R2 v1 2026-06-24T00:53:10.601Z