The number two has many properties in mathematics. An integer is called even if it is divisible by 2. For integers written in a numeral system based on an even number, such as decimal and hexadecimal, divisibility by 2 is easily tested by merely looking at the last digit. If it is even, then the whole number is even. In particular, when written in the decimal system, all multiples of 2 will end in 0, 2, 4, 6, or 8. Two is the smallest and the first prime number, and the only even prime numbe for this reason it is sometimes called the oddest prime). The next prime is three. Two and three are the only two consecutive prime numbers. 2 is the first Sophie German prime, the first factorial prime, the first Lucas prime, the first Ramanujan prime, and the first Smarandache-Wellin prime. It is an Eisenstein prime with no imaginary part and real part of the form 3n - 1. It is also a Stern prime, a Pell number, the first Fibonacci prime, and a Markov number—appearing in infinitely many solutions to the Markov Diophantine equation involving odd-indexed Pell numbers. It is the third Fibonacci number, and the third and fifth Perrin numbers.

Posted on: Fri, 31 Oct 2014 12:30:27 +0000

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