1 (number)

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0 1 2
−1 0 1 2 3 4 5 6 7 8 9
Cardinalone
Ordinal1st
(first)
Numeral systemunary
Factorization1
Divisors1
Roman numeralI
Roman numeral (unicode)Ⅰ, ⅰ
Greek prefixmono- /haplo-
Latin prefixuni-
Binary12
Ternary13
Quaternary14
Quinary15
Senary16
Octal18
Duodecimal112
Hexadecimal116
Vigesimal120
Base 36136
Greek numeralα'
Persian١ - یک
Arabic١
Urdu
Ge'ez
Bengali & Assamese
Chinese numeral一,弌,壹
Korean일, 하나
Devanāgarī
Telugu
Tamil
Kannada
Hebrewא (alef)
Khmer
Thai
Malayalam
Chinese hand sign
Pronunciation of the number 1.

One (1) is a natural number after zero and before two. It represents a single item. A human typically has one {head, nose, mouth, and navel (belly-button)}. The Roman numeral is I.

Mathematics[change | change source]

In mathematics, one is also the only number with this special fact: Any number multiplied by 1 equals that number. Then, the number 1 divides any number but it is not divided by any except itself. The number 1 divides any number to give that same number but it cannot be divided by any other number to give one as the answer. Let n be any number. Then n/1 = n but 1/n is never 1 (when n is not 1). Example: 7/1 = 7, but 1/7 is not 1 (it is 0.142857...).

Any number divided by itself always gives 1 as the answer. n/n = 1 (when n is not 0). Example: 7/7 = 1.

0.999... is a repeating decimal that is mathematically equal to 1. Many proofs have been made to show this is correct.

Computer science[change | change source]

The number one is important for computer science because it is, together with zero, a part of the binary numeral system. In machine code and in many programming languages, one means true and zero means false.

Other meanings[change | change source]

  • In Germany and Austria, one is the grade for "very good". It is the best grade of six possible grades in Germany and the best of five possible grades in Austria. In the Netherlands, one is the lowest grade, and ten the highest and best. In Poland, one is also the lowest grade, but the highest is six.
  • In numerology, the number one is a symbol for everything (unity), the beginning, and God.