225

Number
$225$ (two hundred and twenty-five) is:


 * $2^2 \times 3^2$


 * The $15$th square number after $1$, $4$, $9$, $16$, $25$, $36$, $49$, $64$, $81$, $100$, $121$, $144$, $169$, $196$:
 * $225 = 15 \times 15$


 * The $25$th powerful number after $1$, $4$, $8$, $9$, $16$, $25$, $\ldots$, $108$, $121$, $125$, $128$, $144$, $169$, $196$, $200$, $216$


 * The $9$th octagonal number, after $1$, $8$, $21$, $40$, $65$, $96$, $133$, $176$:
 * $225 = 1 + 7 + 13 + 19 + 25 + 31 + 37 + 43 + 49 = 9 \left({3 \times 9 - 2}\right)$


 * The sum of the first $5$ cubes:
 * $225 = 1^3 + 2^3 + 3^3 + 4^3 + 5^3$