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Encyclopedia > Even and odd numbers

In mathematics, the parity of an object refers to whether it is even or odd. Euclid, Greek mathematician, 3rd century BC, as imagined by by Raphael in this detail from The School of Athens. ...


The formal definition of an odd number is an integer of the form n=2k +1, where k is an integer. The definition of an even number is n=2k where k is an integer. The integers are commonly denoted by the above symbol. ...


Any integer is either even or odd according to the following rules: If it is a multiple of two, it is an even number; otherwise, it is an odd number. Examples of even numbers are −4, 8, 0, and 42. Examples of odd numbers are −3, 9, 1, and 5. The set of even numbers can be written: A multiple of a number is the product of that number with any integer. ... 2 (two) is the natural number following 1 and preceding 3. ... In mathematics, a set can be thought of as any collection of distinct objects considered as a whole. ...

Evens = 2Z = {..., −6, −4, −2, 0, 2, 4, 6, ...}.

The set of odd numbers can be shown like this:

Odds = 2Z + 1 = {..., −5, −3, −1, 1, 3, 5, ...}.

A number (integer) expressed in the decimal numeral system is even or odd according to whether its last digit is even or odd. That is, if the last digit is 1, 3, 5, 7, or 9, then it's odd; otherwise it's even. The same idea will work using any even base. In particular, a number expressed in the binary numeral system is odd if its last digit is 1 and even if its last digit is 0. In an odd base, the number is even according to the sum of its digits - it is even if and only if the sum of its digits is even. The decimal (base ten or occasionally denary) numeral system has ten as its base. ... A numeral is a symbol or group of symbols, or a word in a natural language that represents a number. ... The binary numeral system, or base-2 number system, is a numeral system that represents numeric values using two symbols, usually 0 and 1. ...


The even numbers form an ideal in the ring of integers, but the odd numbers do not — this is clear from the fact that the identity element for addition, zero, is an element of the even numbers only. An integer is even if it is congruent to 0 modulo this ideal, in other words if it is congruent to 0 modulo 2, and odd if it is congruent to 1 modulo 2. In ring theory, a branch of abstract algebra, an ideal is a special subset of a ring which generalizes important properties of integers. ... In ring theory, a branch of abstract algebra, a ring is an algebraic structure in which addition and multiplication are defined and have similar properties to those familiar from the integers. ... In mathematics, the term identity has several important uses: An identity is an equality that remains true regardless of the values of any variables that appear within it, to distinguish it from an equality which is true under more particular conditions. ... Modular arithmetic (sometimes called modulo arithmetic, or clock arithmetic because of its use in the 24-hour clock system) is a system of arithmetic for integers, where numbers wrap around after they reach a certain value — the modulus. ...


All prime numbers are odd, with one exception: the prime number 2. All known perfect numbers are even; it is unknown whether any odd perfect numbers exist. In mathematics, a prime number (or a prime) is a natural number which has exactly two distinct natural number divisors: 1 and itself. ... In mathematics, a perfect number is defined as an integer which is the sum of its proper positive divisors, that is, the sum of the positive divisors not including the number. ...


Goldbach's conjecture states that every even integer greater than 2 can be represented as a sum of two prime numbers. Modern computer calculations have shown this conjecture to be true for integers up to at least 4 × 1014, but still no general proof has been found. Goldbachs conjecture is one of the oldest unsolved problems in number theory and in all of mathematics. ... This article is about the machine. ... In mathematics, a proof is a demonstration that, assuming certain axioms, some statement is necessarily true. ...


The Feit-Thompson theorem states that a finite group is always solvable if its order is an odd number. This is an example of odd numbers playing a role in an advanced mathematical theorem where the method of application of the simple hypothesis of "odd order" is far from obvious. In mathematics, the Feit-Thompson theorem, or odd order theorem, states that every finite group of odd order is solvable. ... In mathematics, a finite group is a group which has finitely many elements. ...


In wind instruments which are cylindrical and in effect closed at one end, such as the clarinet at the mouthpiece, the harmonics produced are odd multiples of the fundamental frequency. (With cylindrical pipes open at both ends, used for example in some organ stops such as the open diapason, the harmonics are even multiples of the same frequency, but this is the same as being all multiples of double the frequency and is usually perceived as such.) See harmonic series (music). A wind instrument is a musical instrument that contains some type of resonator (usually a tube), in which a column of air is set into vibration by the player blowing into (or over) a mouthpiece set at the end of the resonator. ... Two soprano clarinets: a Bâ™­ clarinet (left, with capped mouthpiece) and an A clarinet (right, with no mouthpiece). ... This article is about the components of sound. ... The fundamental tone, often referred to simply as the fundamental, is the lowest frequency in a harmonic series. ... The choir division of the organ at St. ... In a pipe organ, a flue pipe is any pipe that is sounded by a fipple, similar to that in a whistle or a flute a bec, rather than by a beating reed, see reed pipe. ... Pitched musical instruments are usually based on a harmonic oscillator such as a string or a column of air. ...


In number theory, Nielsen proved the following. An odd positive number N such that :σ1(N) / N = n / d ( n,d ∈ N * ) and ω(N)= k is less than  (d+1)^{4^{k}} . Number theory is the branch of pure mathematics concerned with the properties of numbers in general, and integers in particular, as well as the wider classes of problems that arise from their study. ...

Contents

Arithmetic on even and odd numbers

The following laws can be verified using the properties of divisibility. They are a special case of rules in modular arithmetic, and are commonly used to check if an equality is likely to be correct by testing the parity of each side. In mathematics, a divisor of an integer n, also called a factor of n, is an integer which evenly divides n without leaving a remainder. ... Modular arithmetic (sometimes called modulo arithmetic, or clock arithmetic because of its use in the 24-hour clock system) is a system of arithmetic for integers, where numbers wrap around after they reach a certain value — the modulus. ...


Addition and Subtraction

The rules analogous to these for divisibility by 9 are used in the method of casting out nines. 3 + 2 = 5 with apples, a popular choice in textbooks[1] Addition is the mathematical operation of combining or adding two numbers to obtain an equal simple amount or total. ... 5 - 2 = 3 (verbally, five minus two equals three) An example problem Subtraction is one of the four basic arithmetic operations; it is essentially the opposite of addition. ... Casting out nines is a sanity check of the validity of hand computations on integer numbers using +,-,×. It is based on modular arithmetic. ...

  • even ± even = even;
  • even ± odd = odd;
  • odd ± odd = even;

Multiplication

These rules only hold because 2 is a prime number; the analogous rules for divisibility by a composite number would be more complex. In mathematics, multiplication is an elementary arithmetic operation. ... In mathematics, a prime number (or a prime) is a natural number which has exactly two distinct natural number divisors: 1 and itself. ...

  • even × even = even;
  • even × odd = even;
  • odd × odd = odd.

Division

The division of two whole numbers does not necessarily result in a whole number. For example, 1 divided by 4 equals 1/4, which isn't even or odd, since the concepts even and odd apply only to integers. But when the quotient is an integer, it will be even if and only if the dividend has more factors of two than the divisor. In mathematics, especially in elementary arithmetic, division is an arithmetic operation which is the inverse of multiplication. ... It has been suggested that this article or section be merged into Logical biconditional. ... In mathematics, especially in elementary arithmetic, division is an arithmetic operation which is the inverse of multiplication. ...


Parity for other objects

Parity is also used to refer to a number of other properties.

  • The parity of a permutation (as defined in abstract algebra) is the parity of the number of transpositions into which the permutation can be decomposed. For example (ABC) to (BCA) is even because it can be done by swapping A and B then C and A (two transpositions). It can be shown that no permutation can be decomposed both in an even and in an odd number of transpositions. Hence the above is a suitable definition. See the article on even and odd permutations for an elaboration.
  • The parity of a function describes how its values change when its arguments are exchanged with their negatives. An even function, such as an even power of a variable, gives the same result for positive or negative arguments. An odd function, such as an odd power of a variable, gives the negative of its result when given the negative of an argument. It is possible for a function to be neither odd nor even, and for the case f(x) = 0, to be both odd and even.

Permutation is the rearrangement of objects or symbols into distinguishable sequences. ... Abstract algebra is the field of mathematics that studies algebraic structures, such as groups, rings, fields, modules, vector spaces, and algebras. ... In informal language, a transposition is a function that swaps two elements of a set. ... In mathematics, the permutations of a finite set (i. ... In mathematics, even functions and odd functions are functions which satisfy particular symmetry relations, with respect to taking additive inverses. ...

See also


  Results from FactBites:
 
Even and Odd Numbers — FactMonster.com (282 words)
Even numbers are numbers that can be divided evenly by 2.
Odd numbers are numbers that cannot be divided evenly by 2.
Likewise, 8,322 is an even number because it ends in 2.
PlanetMath: even number (92 words)
The concept of even and odd numbers are most easily understood in the binary base.
odd number, even integer, odd integer, even, odd
This is version 7 of even number, born on 2003-09-05, modified 2006-08-10.
  More results at FactBites »

 

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