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What are the first and the last 20 digits of: 7^7^7^7? Any help or hint would be appreciated. Thank you.

 Sep 10, 2019
 #1
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first 20 digits: 73897156067403508131

last 20: 33408341373887572343

 

please correct me if i'm wrong :)

 Sep 10, 2019
 #2
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No, that is not correct!  You must calculate from the RIGHT to LEFT, and not from LEFT to RIGHT.

 

7^7^7^7 =7^7^823,543 =7^[3.7598....x  10^695974 ]

 Sep 11, 2019
 #3
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The first 20 digits are = 7^7^7^7 =7^7^823,543 = 72,390,474,974,388,824,254

 

The last 20 digits are = 7^7^7^7 mod 10^20        =82,879,357,182,733,172,343

 Sep 11, 2019
edited by Guest  Sep 11, 2019

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