HP Forums

http://primes.utm.edu/curios/page.php/41.html

you've been warned...

Incidentally I came across that while looking for a 41-MCODE routine to calculate the sum of digits of a given number - anybody remembers where that'd be?

ironically the 41c is not mentioned.

I don't know about MCODE and the HP-41, but here's a nice little HP-17b solver equation that gives you the sum of digits of a number. It even works on the newer HP-17bii+.

SOD=(I:0:LOG(N):1:MOD(IDIV(N:10^I):10))