Prime numbers and the Sieve of Eratosthenes · Pulse Beat
A prime is a whole number greater than 1 whose only divisors are 1 and itself: 2, 3, 5, 7, 11, 13... Every other whole number above 1 is a product of primes, in exactly one way. That is the fundamenta
A prime is a whole number greater than 1 whose only divisors are 1 and itself: 2, 3, 5, 7, 11, 13... Every other whole number above 1 is a product of primes, in exactly one way. That is the fundamental theorem of arithmetic.
To find all the primes up to 100, use the Sieve of Eratosthenes, about 2,200 years old:
- List the numbers from 2 to 100.
- Circle 2, then cross out all its multiples.
- Circle the next number left, 3, and cross out its multiples.
- Keep going. You only need to continue up to 10, because 10 × 10 = 100.
The numbers still standing are the 25 primes below 100. There are infinitely many primes, which Euclid proved around 300 BC.