Problem 342

The totient of a square is a cube

Consider the number 50.

50^{2} = 2500 = 2^{2} 5^{4}, so φ(2500) = 2 4 5^{3} = 8 5^{3} = 2^{3} 5^{3}. ^{1}

So 2500 is a square and φ(2500) is a cube.

Find the sum of all numbers n, 1 < n 10^{10} such that φ(n^{2}) is a cube.

^{1} φ denotes **Euler's totient function**.

**
These problems are part of
Project Euler
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