841

Number
$841$ (eight hundred and forty-one) is:
 * $29^2$


 * The $29$th square number after $1, 4, 9, 16, 25, 36, \ldots, 625, 676, 729, 784$:
 * $841 = 29 \times 29$


 * The $27$th positive integer which cannot be expressed as the sum of a square and a prime:
 * $1, 10, 25, 34, 58, 64, 85, \ldots, 400, 526, 529, 625, 676, 706, 730, 771, 784, 841, \ldots$