253

Number
$253$ (two hundred and fifty-three) is:
 * $11 \times 23$


 * The $22$nd triangular number after $1, 3, 6, 10, 15, \ldots, 136, 153, 171, 190, 210, 231$:
 * $253 = \displaystyle \sum_{k \mathop = 1}^{22} k = \dfrac {22 \times \left({22 + 1}\right)} 2$


 * The $15$th integer after $7$, $13$, $19$, $35$, $38$, $41$, $57$, $65$, $70$, $125$, $130$, $190$, $205$, $223$ the decimal representation of whose square can be split into two parts which are each themselves square:
 * $253^2 = 64 \, 009$; $6400 = 80^2$, $9 = 3^2$