79

Number
$79$ (seventy-nine) is:


 * The $22$nd prime number


 * The $7$th emirp after $13, 17, 31, 37, 71, 73$


 * The $19$th lucky number:
 * $1, 3, 7, 9, 13, 15, 21, 25, 31, 33, 37, 43, 49, 51, 63, 67, 73, 75, 79, \ldots$


 * The $6$th of $29$ primes of the form $2 x^2 + 29$:
 * $2 \times 5^2 + 29 = 79$