题目70：考察φ(n)是n的一个排列的n值

欧拉计划

Totient permutation

Euler's Totient function, φ(n) [sometimes called the phi function], is used to determine the number of positive numbers less than or equal to n which are relatively prime to n. For example, as 1, 2, 4, 5, 7, and 8, are all less than nine and relatively prime to nine, φ(9)=6.

The number 1 is considered to be relatively prime to every positive number, so φ(1)=1.

Interestingly, φ(87109)=79180, and it can be seen that 87109 is a permutation of 79180.

Find the value of n, 1 < n < , for which φ(n) is a permutation of n and the ratio n/φ(n) produces a minimum.

题目：

欧拉函数 φ(n)（有时也叫做phi函数）可以用来计算小于等于 n 的数字中与 n 互质的数字的个数。例如，因为 1,2,4,5,7,8 全部小于 9 并且与 9 互质，所以φ(9)=6。

数字1被认为与每个正整数互质，所以 φ(1)=1。

有趣的是，φ(87109)=79180，可以看出 87109 是 79180 的一个排列。

对于 1 < n < ，并且 φ(n) 是 n 的一个排列的那些 n 中，使得 n/φ(n) 取到最小的 n 是多少？