Numerology. Numbers. List of numbers. Rational numbers Natural numbers Powers of ten (scientific notation) Integers Notable integers Other numbers that are notable for their mathematical properties or cultural meanings include: Named integers Prime numbers A prime number is a positive integer which has exactly two divisors: one and itself.
Highly composite numbers 1 (number) The glyph used today in the Western world to represent the number 1, a vertical line, often with a serif at the top and sometimes a short horizontal line at the bottom, traces its roots back to the Indians, who wrote 1 as a horizontal line, much like the Chinese character 一.
The Gupta wrote it as a curved line, and the Nagari sometimes added a small circle on the left (rotated a quarter turn to the right, this 9-look-alike became the present day numeral 1 in the Gujarati and Punjabi scripts). The Nepali also rotated it to the right but kept the circle small. This eventually became the top serif in the modern numeral, but the occasional short horizontal line at the bottom probably originates from similarity with the Roman numeral . In some European (e.g., Germany) and Asian (e.g., Israel) countries, the little serif at the top is sometimes extended into a long upstroke, sometimes as long as the vertical line, which can lead to confusion with the glyph for seven in other countries. .
2 (number) 2 (Two; .
3 (number) It is frequently noted by historians of numbers that early counting systems often relied on the three-patterned concept of "One, Two, Many" to describe counting limits.
Early peoples had a word to describe the quantities of one and two, but any quantity beyond was simply denoted as "Many". As an extension to this insight, it can also be noted that early counting systems appear to have had limits at the numerals 2, 3, and 4. References to counting limits beyond these three do not appear to prevail as consistently in the historical record. Three is the largest number still written with as many lines as the number represents. (The Ancient Romans usually wrote 4 as IIII, but this was almost entirely replaced by the subtractive notation IV in the Middle Ages.) . Many world religions contain triple deities or concepts of trinity, including: 4 (number) Four is the second square number, the second centered triangular number.
A number is a multiple of 4 if its last two digits are a multiple of 4. For example, 1092 is a multiple of 4 because 92 = 4×23. 5 (number) Five is the third prime number.
Because it can be written as 221+1, five is classified as a Fermat prime; therefore a regular polygon with 5 sides (a regular pentagon) is constructible with compass and unmarked straightedge. 5 is the third Sophie Germain prime, the first safe prime, the third Catalan number, and the third Mersenne prime exponent. Five is the first Wilson prime and the third factorial prime, also an alternating factorial. Five is the first good prime. It is an Eisenstein prime with no imaginary part and real part of the form . A030452 lists Markov numbers that appear in solutions where one of the other two terms is 5). 6 (number) The SI prefix for 10006 is exa (E), and for its reciprocal atto- (a).
Since six equals the sum of its proper divisors, six is the smallest perfect number, Granville number, and -perfect number. 7 (number) 8 (number) (two cubed), and is the first number of the form All powers of 2 ;( ), have an aliquot sum of one less than themselves.
A number is divisible by 8 if its last 3 digits are also divisible by 8. 8 is the base of the octal number system, which is mostly used with computers. In octal, one digit represents 3 bits. 8 is the only nonzero perfect power that is one less than another perfect power, by Mihăilescu's Theorem. 8 is the order of the smallest non-abelian group all of whose subgroups are normal. 8 and 9 form a Ruth–Aaron pair under the second definition in which repeated prime factors are counted as often as they occur. A polygon with eight sides is an octagon. Sphenic numbers always have exactly eight divisors. 9 (number) In the NATO phonetic alphabet, the digit 9 is called "Niner".Five-digit produce PLU codes that begin with 9 are organic.
Common terminal digit in psychological pricing Nine Lives cat food; its name is derived from the legend that a cat has nine livesNine Network a.k.a. Channel 9, an Australian free-to-air television stationNine West, a clothing brand  Nine (九 pinyin jiǔ) is considered a good number in Chinese culture because it sounds the same as the word "longlasting" (久 pinyin jiǔ).Nine is strongly associated with the Chinese dragon, a symbol of magic and power.
There are nine forms of the dragon, it is described in terms of nine attributes, and it has nine children. 10 (number) 10 (ten A collection of ten items (most often ten years) is called a decade.The ordinal adjective is denary.Increasing a quantity by one order of magnitude is most widely understood to mean multiplying the quantity by ten.To reduce something by one-tenth is to decimate.
(In ancient Rome, the killing of one in ten soldiers in a cohort was the punishment for cowardice or mutiny; or, one-tenth of the able-bodied men in a village as a form of retribution, thus causing a labor shortage and threat of starvation in agrarian societies.)With ten being the base of the decimal system, a scale of 1 to 10 is often used to rank things, as a smaller version of a 1-to-100 scale (as is used in percentages and wine-tasting). Hence, something that scores perfectly is "a perfect ten". A person who is attractive and physically flawless is often said to be "a ten", from the idea of ranking that person's appearance and sex-appeal on a 1-to-10 scale.  11 (number) 11 (eleven In English, it is the smallest positive integer requiring three syllables and the largest prime number with a single-morpheme name. Its etymology originates from a Germanic compound ainlif meaning "one left".). If a number is divisible by 11, reversing its digits will result in another multiple of 11.
As long as no two adjacent digits of a number added together exceed 9, then multiplying the number by 11, reversing the digits of the product, and dividing that new number by 11, will yield a number that is the reverse of the original number. (For example: 142,312 x 11 = 1,565,432. 2,345,651 / 11 = 213,241.) 12 (number) 12 (twelve A group of twelve things is called a duodecad. The ordinal adjective is duodecimal, twelfth. Numbers. A notational symbol that represents a number is called a numeral. In addition to their use in counting and measuring, numerals are often used for labels (telephone numbers), for ordering (serial numbers), and for codes (e.g., ISBNs). Classification of numbers Natural numbers The most familiar numbers are the natural numbers or counting numbers: 1, 2, 3, and so on.
Mighty Number. Numerology.