Tony Padilla on Harshad Numbers. Learn for free on Brilliant (and get 20% off a premium subscription) at https://brilliant.org/numberphile (episode sponsor). More links & stuff in full description below ↓↓↓

Extra footage from this interview can be found on Numberphile2 - https://youtu.be/iGEC1FH5yBU

Harshad Numbers are also known as Niven Numbers.

Tony Padilla's book Fantastic Numbers and Where to Find Them - https://amzn.to/3VywNyy

More from Tony on Numberphile - https://www.youtube.com/playlist?list=PLt5AfwLFPxWL8KAJKO3WfHhJcWrJfjgfU

Plus Tony on Sixty Symbols - https://www.youtube.com/playlist?list=PLcUY9vudNKBPJmX64Jay51cdZTKMz4ACs

Here's a Harshad Tester (for various bases) based on Tony's code: https://www.numberphile.com/is-it-a-harshad-number (sorry for an problems, I was kind of experimenting here)

On Consecutive Niven Numbers (paper): https://www.fq.math.ca/Scanned/31-2/cooper.pdf

Additive bases and Niven numbers (paper): https://arxiv.org/abs/2101.07593

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Used some AI to represent the old greats doing math in the offices.