Question 1207597
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Find the greatest prime divisor of the value of the arithmetic series
5 + 6 + 7 + \dots + 135.
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<pre>
This sum, as for any arithmetic progression, is the product of the mean by the number of terms.


The mean is  {{{(5+135)/2}}} = {{{140/2}}} = 70.

The number of terms is  135-4 = 131.


So, the sum is  70*131.


Decomposition of the sum to product of primes is  70*131 = 2*5*7*131.


The greatest prime divisor is 131.


<U>ANSWER</U>.  The greatest prime divisor is 131.
</pre>

Solved.


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