A Venn Diagram is a powerful visual way to show the factors of a number, and the common factors of two numbers. Nice implementation.

Here is the home page for this activity
http://www.teacherled.com/2009/01/31/venn-factors/

The learning activity can be found at:
http://www.teacherled.com/resources/vennfactors/vennfactorload.html

**

Here are the comparable Venn Diagram resources for multiples:

Home page
http://www.teacherled.com/2009/01/27/venn-multiples/

And the learning resource
http://www.teacherled.com/resources/vennmultiples/vennmultipleload.html

Four activities to support the teaching and learning of Factors and Multiples.

The Factor Game
This is the classic factor game.

Highest Common Factor Game
A great game for practising highest common factors.

Factors and Multiples Puzzle (from NRich)
A fantastic whole number activity from the NRich website. Factors, multiples, square numbers, triangular numbers, etc.

Juniper Green
A great game for consolidating factors and multiples.

There is a cool puzzle at the Nrich website called the Factors and Multiples Puzzle, which can be found on-line at http://nrich.maths.org/public/viewer.php?obj_id=5448

I have created a flipchart to support the use of this puzzle in the classroom. Enjoy!

Choose your starting number. Then click repeatedly on only those ghosts which are multiples of that number. How long does it take to reach 100?
Three thumbs up!

http://www.oswego.org/ocsd-web/games/Ghostblasters1/gbcd.html

Prime Factors Calculator
Type in a number (it can be a large number but not TOO large) and click {OK} to see its prime factors.
http://newmanservices.com/primefact/

The Nth Prime Number
Enter a value for n below, from 1 to 10^12, inclusive. The server will return the nth prime number (counting 2 as the first). Commas and scientific notation (e.g. 1.0e12) are allowed.
http://primes.utm.edu/nthprime/index.php#nth

Factorise
Visualize factors through building rectangular areas on a grid. First enter all the factorizations of a number, then draw each factor set as an area on the grid. Factorize is one of the Interactivate assessment explorers.

http://www.shodor.org/interactivate/activities/Factorize/

Factorise II
Visualize factors through building rectangular areas on a grid. As you draw each factor set on the grid, the factors will be listed.

http://www.shodor.org/interactivate/activities/FactorizeTwo/

An interactive 100 square. You can choose to start the square with either 0 or 1.
http://www.hellam.net/maths2000/100square.html

You can also change the 'width' of the 100 board using this link:
http://www.hellam.net/maths2000/nsquare.html

Here is a different 100 square. Clink on the IDEAS button to see how you might use this tool.
http://www.amblesideprimary.com/ambleweb/mentalmaths/countersquare.html

Click on two cards to turn them over. If they match, they are cleared from the board. If not, they remain on the board. How many turns will it take you to clear the board? But there is a twist - you also have to click on the 'odd number out'!

http://www.interactivestuff.org/match/maker.phtml?featured=1&id=17

A highly interactive Promethean ActivBoard flipchart where students discover the prime numbers, factors of numbers and the Highest Common Factor using a game based on Eratosthenes Sieve. Three thumbs up!

The flipchart can be found here:
http://www.prometheanplanet.com/uk/server/show/ConResource.13015

If you are not yet a member of Promethean Planet, you will first have to register here:
http://www.prometheanplanet.com/uk/server/show/nav.914

If you want to view the activities and have some interactivity with them, but you don't have the ActivStudio software, you can download the free Viewer from here:
http://www.mypromethean.com/uk/server/show/ConWebDoc.2974

Join together cogs of different sizes and investigate what happens when you turn them. From the NRich website.
http://nrich.maths.org/public/viewer.php?obj_id=4771&part=note