Funny exponent (Part 1)

What are the last seven digits of 9 1 , 000 , 000 9^{1,000,000} ?

Note : Ignore initial zeroes of the answer for example if the answer is 0002456 then submit 2456.


Inspiration


The answer is 1.

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1 solution

Chew-Seong Cheong
May 18, 2020

9 1 0 6 ( 10 1 ) 1 0 6 ( 1 0 1 0 6 1 0 1 0 6 + 5 + 1 0 7 + 1 ) 1 (mod 1 0 7 ) \large 9^{10^6} \equiv (10 -1)^{10^6} \equiv \left(10^{10^6} - 10^{10^6+5} + \cdots - 10^7 + 1 \right) \equiv \boxed 1 \text{ (mod }10^7)

Good solution!

Zakir Husain - 1 year ago

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Glad that you like it.

Chew-Seong Cheong - 1 year ago

Very elegant solution!

Veselin Dimov - 4 months, 2 weeks ago

Sir I am unable to understand the factorisation, can you please explain it?

Vinayak Srivastava - 2 months, 1 week ago

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The expansion is done using Binomial Theorem I guess

Zakir Husain - 2 months, 1 week ago

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Ohk, maybe I get it now. Thanks!

Vinayak Srivastava - 2 months, 1 week ago

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