425
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Number
$425$ (four hundred and twenty-five) is:
- $5^2 \times 17$
- The $2$nd positive integer after $325$ which can be expressed as the sum of two square numbers in $3$ distinct ways:
- $425 = 20^2 + 5^2 = 19^2 + 8^2 = 16^2 + 13^2$
- The $17$th pentagonal number after $1$, $5$, $12$, $22$, $35$, $51$, $70$, $92$, $117$, $145$, $176$, $210$, $247$, $287$, $330$, $376$:
- $425 = \ds \sum_{k \mathop = 1}^{17} \paren {3 k - 2} = \dfrac {17 \paren {3 \times 17 - 1} } 2$
- The $33$rd generalized pentagonal number after $1$, $2$, $5$, $7$, $12$, $15$, $\ldots$, $222$, $247$, $260$, $287$, $301$, $330$, $345$, $376$, $392$:
- $425 = \ds \sum_{k \mathop = 1}^{17} \paren {3 k - 2} = \dfrac {17 \paren {3 \times 17 - 1} } 2$