247
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Number
$247$ (two hundred and forty-seven) is:
- $13 \times 19$
- The $13$th pentagonal number after $1$, $5$, $12$, $22$, $35$, $51$, $70$, $92$, $117$, $145$, $176$, $210$:
- $247 = 1 + 4 + 7 + 10 + 13 + 16 + 19 + 22 + 25 + 28 + 31 + 34 + 37 = \dfrac {13 \paren {3 \times 13 - 1} } 2$
- The $25$th generalized pentagonal number after $1$, $2$, $5$, $7$, $12$, $15$, $\ldots$, $100$, $117$, $126$, $145$, $155$, $176$, $187$, $210$, $222$:
- $247 = \dfrac {13 \paren {3 \times 13 - 1} } 2$
- The $48$th positive integer $n$ such that no factorial of an integer can end with $n$ zeroes.