Consider the number 50. 502 = 2500 = 22 × 54, so φ(2500) = 2 × 4 × 53 = 8 × 53 = 23 × 53. 1 So 2500 is a square and φ(2500) is a cube.
Find the sum of all numbers n, 1 < n < 1010 such that φ(n2) is a cube.
1 φ denotes Euler's totient function.