Number Recreations

Shyam Sunder Gupta
Former Principal Chief Engineer,
North Western Railway, Jaipur, India-302017

What is New? (Update 12 April, 2021)

The page on Amicable Numbers updated.

The page on Fascinating Triangular Numbers updated.

The page on Unlucky 13 updated.

CYF NO. 53 Solution by Al Zimmermann and Brian Trial given.

CYF NO. 49 Comments by Daniel Suteu given.

Prime curios 62,102,181,199,293,373,881,993, 1524,1609,3527,6031,6691,7740,7757,9257,9647 and many more added.

Do You Know?

216 = 65536 is the only known power of 2 in which no digit is a power of 2.

Can You Find?

CYF NO. 54
The smallest number n such that Eulers Trinomial   n*n + n + 41  gives a Strong Pseudoprime (base-2).

email your answer


Note: The above topics including many more will be added in due course.


My Contributions in Prime Curios

Prime Curios! - site maintained by G. L. Honaker Jr. and Chris Caldwell

My Favorite Links

  • Magic Squares,Magic Stars and Other Interesting number patterns by Harvey Heinz
  • Mudd Math Fun Facts pages
  • On-Line Encyclopedia of Integer Sequences OEIS
  • Math Puzzles
    An interesting site with lot of math recreations by Ed Pegg Jr.

My Favorite Books

Recommended list of books for those interested in Recreational and Computational Number theory
In Association with In Association with

The Rail
(January, 2003)

(March, 2003)
The Busy Educator Award
(October, 2003)

Send me e-mail at

This page was last updated on 12th April, 2021.

Copyright 2001-2021 Shyam Sunder Gupta. All rights reserved.