Can Euler help you?

Find the last 2 digits of

3333 4444 \huge \color{#624F41}{3333}^{\color{#EC7300}{4444}}


The answer is 21.

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2 solutions

Anish Harsha
Nov 27, 2015

We note that finding the last two digits of 333 3 4444 3333^{4444} can be obtained by reducing 333 3 4444 ( m o d 100 ) 3333^{4444}\pmod {100} . Since, ( 3333 , 100 ) = 1 (3333,100) = 1 , we can apply this theorem.

We first calculate that ϕ ( 100 ) = ϕ ( 2 2 ) ϕ ( 5 2 ) = ( 2 ) ( 5 ) ( 4 ) = 40 \phi(100) =\phi(2^2)\phi(5^2)=(2)(5)(4)=40 . Hence, it follows the Euler's theorem that 333 3 40 1 ( m o d 100 ) 3333^{40}\equiv 1 \pmod{100} . Now let's apply the division algorithm on 4444 and 40 as follows :
4444 = 40 ( 111 ) + 4 4444=40(111)+4

Hence, it follows that: 333 3 4444 ( 333 3 40 ) 111 . 333 3 4 ( 1 ) 111 . 333 3 4 ( m o d 100 ) 3 3 4 1185921 21 ( m o d 100 ) 3333^{4444} \equiv (3333^{40})^{111}. 3333^4 \equiv (1)^{111}.3333^4 \pmod{100} \equiv 33^4 \equiv 1185921 \equiv 21 \pmod{100}

Hence the last two digits are 2 and 1.

Akshat Sharda
Nov 27, 2015

333 3 4444 = 3 4444 111 1 4444 ( 3 4 ) 1111 111 1 4444 = 8 1 1111 111 1 4444 Now finding last 2 digits : 81 41 = 33 21 3333^{4444}=3^{4444}\cdot 1111^{4444} \\ (3^{4})^{1111}\cdot 1111^{4444}=81^{1111}\cdot 1111^{4444} \\ \text{Now finding last 2 digits : }81\cdot 41=33\boxed{21}

How I found last 2 digits ?

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