Armstrong

http://archive.li/56WdF
https://web.archive.org/web/20100124175046/http://homepages.cwi.nl:80/~dik/english/mathematics/armstrong.html
http://www.adahome.com/Discover/Examples/PDI/
https://www.deimel.org/rec_math/DI_0.htm
http://www.m-brella.be/math/topics/NarcissisticNumber.html
https://www.primepuzzles.net/puzzles/puzz_015.htm
https://web.archive.org/web/20100124175046/http://homepages.cwi.nl:80/~dik/english/mathematics/armstrong.html