Guess the prime factors - 2

Find the largest prime factor of the integer 999,999,995,904.


The answer is 601.

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1 solution

Julian Yu
Dec 24, 2016

The given number is slightly less than 10 12 {10}^{12} and is in fact 10 12 4096 = 10 12 2 12 {10}^{12}-4096={10}^{12}-{2}^{12} .

This factors as 2 12 ( 5 12 1 ) {2}^{12}({5}^{12}-1) and 5 12 1 = ( 5 3 + 1 ) ( 5 3 1 ) ( 5 2 + 1 ) ( 5 4 5 2 + 1 ) {5}^{12}-1=({5}^{3}+1)({5}^{3}-1)({5}^{2}+1)({5}^{4}-{5}^{2}+1)

= ( 5 1 ) ( 5 2 + 5 + 1 ) ( 5 + 1 ) ( 5 2 5 + 1 ) ( 5 2 + 1 ) ( 5 4 5 2 + 1 ) =(5-1)({5}^{2}+5+1)(5+1)({5}^{2}-5+1)({5}^{2}+1)({5}^{4}-{5}^{2}+1)

= 2 2 31 2 3 3 7 2 13 601 ={ 2 }^{ 2 }\cdot 31\cdot 2\cdot 3\cdot 3\cdot 7\cdot 2\cdot 13\cdot 601

Thus, the given number is 2 16 3 2 7 13 31 601 { 2 }^{ 16 }\cdot { 3 }^{ 2 }\cdot 7\cdot 13\cdot 31\cdot 601 and its largest prime factor is 601 \boxed{601} .

Same solution! :D

Do you still remember me TT.TT

Manuel Kahayon - 4 years, 5 months ago

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