We're very proud to be number three and thought you may be interested in the following facts about this special number from Wikipedia:
- Three is the first odd prime number, and the second smallest prime. It is both the first Fermat prime (22n + 1) and the first Mersenne prime (2n − 1), as well as the first lucky prime. However, it's the second Sophie Germain prime, the second Mersenne prime exponent, the second factorial prime (2! + 1), the second Lucas prime, the second Stern prime.
- Three is the first unique prime due to the properties of its reciprocal.
- Three is the aliquot sum of 4.
- Three is the third Heegner number.
- Three is the second triangular number and it is the only prime triangular number. Three is the only prime which is one less than a perfect square. Any other number which is n2 − 1 for some integer n is not prime, since it is (n − 1)(n + 1). This is true for 3 as well, but in its case one of the factors is 1.
- Three non-collinear points determine a plane and a circle.
- Three is the fourth Fibonacci number and the third that is unique. In the Perrin sequence, however, 3 is both the zeroth and third Perrin numbers.
- Three is the fourth open meandric number.
- Vulgar fractions with 3 in the denominator have a single digit repeating sequences in their decimal expansions, (.000..., .333..., .666...)