529

Number
$529$ (five hundred and twenty-nine) is:
 * $23^2$


 * The $23$rd square number after $1, 4, 9, 16, 25, 36, \ldots, 361, 400, 441, 484, 529$:
 * $529 = 23 \times 23$


 * The $20$th positive integer which cannot be expressed as the sum of a square and a prime:
 * $1, 10, 25, 34, 58, 64, 85, 91, 121, 130, 169, 196, 214, 226, 289, 324, 370, 400, 526, 529, \ldots$