0

Number
$0$ (zero) is:


 * The only number which is both positive and negative


 * The only integer which is divisible by $0$


 * The only integer which is divisible by all integers


 * The identity element for the operation of addition


 * The zero element for the operation of multiplication


 * The value of $\log_b 1$ for all bases $b$


 * The $0$th (and therefore smallest) cardinal number


 * The $0$th (and therefore smallest) ordinal number


 * The $0$th Fibonacci number


 * The $0$th triangular number:
 * $0 = \dfrac {0 \paren {0 + 1} } 2$


 * The $1$st subfactorial:
 * $0 = 1! \paren {1 - \dfrac 1 {1!} }$


 * The $1$st integer $m$ such that $m! + 1$ (its factorial plus $1$) is prime:
 * $0! + 1 = 1 + 1 = 2$


 * The $1$st integer such that its double factorial plus $1$ is prime:
 * $0!! + 1 = 2$


 * The $1$st integer $n$ such that $2^n$ contains no zero in its decimal representation:
 * $2^0 = 1$


 * The $1$st integer $n$ such that $5^n$ contains no zero in its decimal representation:
 * $5^0 = 1$


 * The $1$st integer $n$ such that both $2^n$ and $5^n$ have no zeroes:
 * $2^0 = 1, 5^0 = 1$


 * The $1$st integer which is palindromic in both decimal and binary:
 * $0_{10} = 0_2$


 * The $1$st integer which is palindromic in both decimal and ternary:
 * $0_{10} = 0_3$


 * The $1$st number which is (trivially) the sum of the increasing powers of its digits taken in order:
 * $0^1 = 0$


 * The $1$st integer $m$ such that $m^2 = \dbinom n 0 + \dbinom n 1 + \dbinom n 2 + \dbinom n 3$ for integer $n$:
 * $0^2 = \dbinom {-1} 0 + \dbinom {-1} 1 + \dbinom {-1} 2 + \dbinom {-1} 3$


 * The $1$st of the $5$ Fibonacci numbers which are also triangular


 * The $1$st palindromic triangular number


 * The $1$st palindromic integer which is the index of a palindromic triangular number
 * $T_0 = 0$


 * The $1$st Ramanujan-Nagell number:
 * $0 = 2^0 - 1 = \dfrac {0 \paren {0 + 1} } 2$


 * The $1$st of the $3$ Fibonacci numbers which equals its index


 * The $1$st Dudeney number:
 * $0^3 = 0$


 * The $1$st non-negative integer $n$ such that the Fibonacci number $F_n$ ends in $n$


 * The $1$st of the only $2$ integers which are equal to the sum of the squares of their digits when expressed in base $10$:
 * $0 = 0^2$


 * The $2$nd integer $n$ after $-1$ such that $\dbinom n 0 + \dbinom n 1 + \dbinom n 2 + \dbinom n 3 = m^2$ for integer $m$:
 * $\dbinom 0 0 + \dbinom 0 1 + \dbinom 0 2 + \dbinom 0 3 = 1^2$

Also see

 * Zero Divides Zero
 * Integer Divides Zero
 * General Logarithm of 1 is 0