Khan Academy
Khan Academy: Prime Numbers
Prime numbers are numbers that have only 2 factors: 1 and themselves. For example, the first 5 prime numbers are 2, 3, 5, 7, and 11. By contrast, numbers with more than 2 factors are called composite numbers.
Khan Academy
Khan Academy: Recognizing Prime and Composite Numbers
Can you recognize the prime numbers in this group of numbers? Which are prime, composite, or neither?