1801

Number
$1801$ (one thousand, eight hundred and one) is:
 * The $279$th prime number


 * The $25$th centered hexagonal number after $1, 7, 19, 37, 61, 91, 127, \ldots, 817, 919, 1027, 1141, 1261, 1387, 1519, 1657$:
 * $1801 = \displaystyle 1 + \sum_{k \mathop = 1}^{25 - 1} 6 k = 25^3 - 24^3$