emirp
(another Prime Pages' Glossary entries)
The Prime Glossary
Glossary: Prime Pages: Top 5000: When you reverse the digits of most primes you get a composite (43 becomes 34).  Of course a palindromic prime reads the same forward and backwards, so reversing a palindromic prime gives you a prime.  An emirp (prime spelled backwards) is a prime that gives you a different prime when its digits are reversed.  The sequence of emirps begins:
13, 17, 31, 37, 71, 73, 79, 97, 107, 113, 149, 157, 167, 179, 199, 311, 337, 347, 359, 389, 701, 709, 733, 739, 743, 751, 761, 769, 907, 937, 941, 953, 967, 971, 983, 991, 1009, 1021, 1031, 1033, 1061, 1069, 1091, 1097, 1103, 1109, 1151, 1153, 1181, 1193

Related pages (outside of this work)

References:

Gardner85 (p. 230)
M. Gardner, Magic numbers of Dr. Matrix, Prometheus Books, 1985.  ISBN 0879752823.



Chris K. Caldwell © 1999-2014 (all rights reserved)