676

Number
$676$ (six hundred and seventy-six) is:
 * $2^2 \times 13^2$


 * The $26$th square number after $1, 4, 9, 16, 25, 36, \ldots, 361, 400, 441, 484, 529, 576, 625$:
 * $676 = 26 \times 26$


 * The $22$nd positive integer which cannot be expressed as the sum of a square and a prime:
 * $1, 10, 25, 34, 58, 64, 85, 91, 121, 130, 169, 196, 214, 226, 289, 324, 370, 400, 526, 529, 625, 676, \ldots$