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If you are the account owner, please submit ticket for further information. This article is about tutorial. English for children number. For the year, see AD 2. It is the natural number following 1 and preceding 3.

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, hexadecimal, or in any other base that is even, divisibility by 2 is easily tested by merely looking at the last digit. Two and three are the only two consecutive prime numbers. This binary number system is used extensively in computing. The number of up-arrows refers to the level of the hyperoperation. Two is the only number x such that the sum of the reciprocals of the powers of x equals itself. Powers of two are central to the concept of Mersenne primes, and important to computer science.

Two is the first Mersenne prime exponent. Taking the square root of a number is such a common mathematical operation, that the spot on the root sign where the exponent would normally be written for cubic and other roots, may simply be left blank for square roots, as it is tacitly understood. The square root of 2 was the first known irrational number. The smallest field has two elements. This latter set is important in category theory: it is a subobject classifier in the category of sets. In any n-dimensional, euclidean space two distinct points determine a line.