1 (number)

← 0 1 2 →
−1 0 1 2 3 4 5 6 7 8 9 → ← 0 10 20 30 40 50 60 70 80 90 →
Cardinal	one
Ordinal	1st (first)
Factorization	1
Divisors	1
Roman numeral	I
Roman numeral (unicode)	Ⅰ, ⅰ
Greek prefix	mono- /haplo-
Latin prefix	uni-
Binary	12
Ternary	13
Quaternary	14
Quinary	15
Senary	16
Octal	18
Duodecimal	112
Hexadecimal	116
Vigesimal	120
Base 36	136
Greek numeral	α'
Persian	١ - یک
Arabic	١
Urdu
Ge'ez	፩
Bengali & Assamese	১
Chinese numeral	一，弌，壹
Korean	일, 하나
Devanāgarī	१
Telugu	೧
Tamil	௧
Kannada	೧
Hebrew	א (alef)
Khmer	១
Thai	๑
Malayalam	൧

Chinese hand sign

File:En-us-One.ogg 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

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 but 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.

Computer science

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 lots of programming languages one means true. Zero means false.

Other meanings

• 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.