1. x=the number of even digits, y=the number of odd digits, z=the total number digits.
2. Concatenate to create the number xyz (a leading zero is ok if x=0)

[Example: 12345678901 has x=5, y=6, z=11 for step 1 and 5611 for step 2]

3. Repeat steps 1 and 2 of this process until your number is unchanged.

What number(s) will the process terminate at?
Will the process always terminate?
Find a 20 digit starting number that terminates in the maximum number of steps (among 20 digit numbers.)

I had the same question, but hidden in the example is the fact that 0 is counted as even in this example. But even if 0 was counted as neither, it would turn into 205.

Since 0 is even, all even or all odd ->02020->505->213->123->123