1 (number) facts for kids

Quick facts for kids ← 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)
Numeral system	unary
Factorization	1
Divisors	1
Greek numeral	Α´
Roman numeral	I
Roman numeral (unicode)	Ⅰ, ⅰ
Greek prefix	mono- /haplo-
Latin prefix	uni-
Binary	12
Ternary	13
Senary	16
Octal	18
Duodecimal	112
Hexadecimal	116
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
counting rod	𝍠

A Chinese hand sign for the number one.

One (1) is a natural number. It comes right after zero and before two. It helps us count a single item or thing. For example, a person usually has one head, one nose, and one mouth. The Roman numeral for one is I.

The Number One in Math

In mathematics, the number 1 is very special. It's known as the "multiplicative identity." This means that when you multiply any number by 1, the number stays the same. It's also the only number with these unique features:

• If you multiply any number n by 1, the answer is always n. For example, 7 × 1 = 7.
• If you divide any number n by 1, the answer is always n. For example, 7 / 1 = 7.
• If you divide any number n (except 0) by itself, the answer is always 1. For example, 7 / 7 = 1.
• You cannot divide 1 by any other natural number (except 1 itself) and get another whole natural number as the result.

The Number One in Computers

The number one is very important in computer science. This is because computers use the binary system, which only uses two numbers: 1s and 0s. In machine code and many programming languages, the number one often means "true" or "on," while zero means "false" or "off." This simple system helps computers process information.

Related Pages

• Zero