Sieve of Eratosphenes

Named after the Greek Mathematician Erastosthenes, the sieve provides a very efficient method for finding prime numbers. As well as finding primes, the process helps students learn about multiples and factors. This interactive sieve is unique in that it show more than one color per square. This allows for the sieve to be used in variety of interesting ways. For example the Sieve can be used to find the the LCM ( Lowest/Least common multiple ) of a set of numbers. A youtube video describes how to use this app, and also full help and instructions can be displayed by clicking the info icon.

Screenshots from Chrome Web Store