Number Recreations

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

What is New? (Update 14 March, 2022)

The page on The Number of the Beast 666 added.

The page on Fascinating Triangular Numbers updated.

CYF NO. 55 Contribution by Al Zimmermann, Maximilian and Giorgos Kalogeropoulos given.

Prime curios 17, 25, 94, 111, 587, 1111, 3527, 11956, 122265, 314159, 912673, 962963, 5261941, 5794777, 4592307816, 7775737169, 97959391, 9876541023, 9876542103, 141592653589, 41434547495153, 3637383940414243, 4936251694114916253649, 34149...97531 (39-digits), 72951...12729 (41-digits), 46260...12101(56-digits), 78583...21291 (70-digits), 36132...24361(90-digits), 57137...97531 (209-digits), 12491...11753 (216-digits), 14159...07021 (547-digits), 42574...61941 (948-digits), 76937...11753 (1998-digits), 21309...67281 (5062-digits) and 72180...10631 (6560-digits) added.

Integer Sequences A350755, A350368, A350367, A349696, A350304, A350303, A349773, A349722, A349774, A349539 added.

Do You Know?

Except 1 and 9, there is no perfect square with all of its digits odd.

Can You Find?

CYF NO. 56
The smallest amicable pair (m, n) such that digital root of pair sum (i.e. m + n) is 4.

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 14th March, 2022.

Copyright 2021-2022 Shyam Sunder Gupta. All rights reserved.