10^6 has 7 digits

100^6 has 13 digits

Our number has 9 digits and ends in 5

So x is a 2 digit number ending in 5 and closer to 10 than to 100.

Judging from the number of digits, x is probably 25.

20^6 = 64,000,000

30^6 = 729,000,000

So x must be 25.

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Here are some other ways to look at it:

We note that our number is 1 mod 3.

We want a 2 digit number, ending in 5 which, when raised to the 6th power is 1 mod 3.

But 5 itself is 2 mod 3; successive powers of 2 alternate between 2 and 1 mod 3. So the first digit could be either 1 or 2 (mod 3).  This rules out 35, 65, 95

The first digit can be:  1, 2, 4, 5, 7, 8

or

Consider √10 * 10: approx 31.6. Square it: 1000;  Cube that: 10^9 which is 10 digits.  But our number is only 9 digits.

Our number must be less than 31.6