De Polignac's Formula/Examples/11 in 1000
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Example of Use of De Polignac's Formula
The prime factor $11$ appears in $1000!$ to the power of $98$.
That is:
- $11^{98} \divides 1000!$
but:
- $11^{99} \nmid 1000!$
Proof
Let $\mu$ denote the power of $11$ which divides $1000!$
\(\ds \mu\) | \(=\) | \(\ds \sum_{k \mathop > 0} \floor {\frac {1000} {11^k} }\) | De Polignac's Formula | |||||||||||
\(\ds \) | \(=\) | \(\ds \floor {\frac {1000} {11} } + \floor {\frac {1000} {121} }\) | ||||||||||||
\(\ds \) | \(=\) | \(\ds 90 + 8\) | ||||||||||||
\(\ds \) | \(=\) | \(\ds 98\) |
$\blacksquare$