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Summing or Multiplying (Posted on 2006-08-21) Difficulty: 4 of 5
123 is a peculiar integer, because 1+2+3=1*2*3. 1412 is also peculiar, since 1+4+1+2=1*4*1*2.

A simple question: are there infinitely many such numbers?

A not so simple question: if so, are there such numbers for ANY number of digits?

See The Solution Submitted by e.g.    
Rating: 4.2500 (8 votes)

Comments: ( Back to comment list | You must be logged in to post comments.)
re(3): Peculiars vs. Primes | Comment 18 of 21 |
(In reply to re(2): Peculiars vs. Primes by Dej Mar)

Dej Mar, your reasoning for comparing two infinite sets is a bit faulty. Consider the set of naturals (positive integers) and the set of all integers. They are considered to have as many elements (even if one of them is a strict subset of the other) because you can create a one-to-one mapping from one set to the other. Being a subset does not imply having less elements if you're talking about infinite sets. For example, the number of rational numbers is also the same as the number of integers. Very fascinating stuff :-).

Except for this detail, I agree with your statement: there are differences between infinities, and probably there are more primes than peculiars.

  Posted by Robby Goetschalckx on 2006-08-23 05:14:50

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