Today we can to the end of our short project on divisors. The topic for today was finding a formula for the sum of the divisors of an integer. 243 more words

## Tags » Primes

#### A neat problem Dan Anderson shared with us

We’ve spent the last couple of days studying divisors of integers – mainly the number of divisors and the sum of those divisors. This topic came to us via a “things you should know for math contests” list that math team at my older son’s school gave to the kids. 337 more words

#### Exploring Sums of Divisors with kids

This project is the second in week long series about some topics that my son’s math club will be studying at school. The topic for today is sums of divisors of a positive integer. 371 more words

#### The Mystifying 73,939,133

Prime’s the case again…

This number, ** 73,939,133** is completely marvelous… It has a mystifying property…

**If you keep on removing the last digit here , the resulting number shall be a prime at each step.** 81 more words

#### A Problem on Number of Divisors

This is a problem I created in . I proposed it to be used here as problem . Though initially I was a bit careless with the bounds, but just to be safe, I am proving the weak bound here. 367 more words

#### The Fool-proof Prime Test

It’s been a long time since mathematicians have discovered tests ( or equations as you like it ) for searching and exploring new primes…

But most of them are faulty and do go wrong somewhere. 190 more words

#### On a Posa like Inequality

In this post we proved Posa’s inequality. Now I am interested in finding the largest exponent so that

for some given .

I have already found a bound on this, though it’s really ugly. 20 more words