positive integers
Number Theory
Level
pending
Find the number of positive integers 2000 that are coprime integers with 2000.
The answer is 800.
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1 solution
2000 = 2^4 x 5^3. And phi(2000) = 2000(1 - 1/2)(1 - 1/5) = 2000(1/2)(4/5)= 800.