[b]Definition:[/b] A [b]prime number [/b]is a positive integer [math]p>1[/math] that has no positive integer divisors other than [math]1[/math] and [math]p[/math] itself. More concisely, a prime number [math]p[/math] is a positive integer having exactly one positive divisor other than [math]1[/math], meaning it is a number that cannot be factored.[br]Positive integers other than 1 which are not prime are called [b]composite numbers[/b].[br][br][b]Example:[/b] the only divisors of [math]13[/math] are [math]1[/math] and [math]13[/math], making [math]13[/math] a prime number, while the number [math]24[/math] has divisors [math]1,2,3,4,6,8,12[/math], and [math]24[/math] (corresponding to the factorization [math]24=2^3\cdot3[/math]), making [math]24[/math] not a prime number.

The purpose of the applet below is to sort out prime numbers from composite numbers.[br]Click on the squares that contain prime numbers and then click on check.[br]Try it as many times as you may need.

[url=https://mathworld.wolfram.com/PrimeNumber.html][i]Animated Factorization Diagrams – Data Pointed[/i]. Data Pointed RSS. (n.d.). http://www.datapointed.net/visualizations/math/factorization/animated-diagrams/. [br][br]amelka12. (2019, October 14). [i]Kopia Liczby pierwsze / Prime numbers[/i]. GeoGebra. https://www.geogebra.org/m/ntrhsppk. [br][br][br][/url]Weisstein, Eric W. "Prime Number." From [url=https://mathworld.wolfram.com/][i]MathWorld[/i][/url]--A Wolfram Web Resource. [url=https://mathworld.wolfram.com/PrimeNumber.html]https://mathworld.wolfram.com/PrimeNumber.html[br][br][/url][url=https://mathworld.wolfram.com/about/author.html]Vuković, A. M. (n.d.). [i]Sieve of Eratosthenes[/i]. GeoGebra. https://www.geogebra.org/m/uGX53dy7. [br][br]Wikimedia Foundation. (2021, July 16). [i]Sieve of Eratosthenes[/i]. Wikipedia. https://en.wikipedia.org/wiki/Sieve_of_Eratosthenes. [br][/url]