1089

Number
$1089$ (one thousand and eighty-nine) is:
 * $3^2 \times 11^2$


 * The $33$rd square number after $1, 4, 9, 16, 25, 36, \ldots, 625, 676, 729, 784, 841, 900, 961, 1024$:
 * $1089 = 33 \times 33$


 * Take a $3$-digit number, reverse it and subtract the smaller from the larger, reverse that and add it to itself, and you end up with $1089$.


 * The $29$th positive integer which cannot be expressed as the sum of a square and a prime:
 * $1, 10, 25, 34, 58, 64, 85, \ldots, 706, 730, 771, 784, 841, 1024, 1089, \ldots$

Also see

 * 1089 Trick