Problem - 4152
Let $N$ be a square number. If its units digit is neither $4$ nor $6$, then its tens digit must be even.
First, by # 4149, if its unit digit is odd, its tens digit must be even.
When $N$ is an even square but ends with neither $4$ nor $6$, then it must end with $0$. Meanwhile, an even square must be a multiple of $4$. Therefore, its tens digit must be even in order to satisfy this requirement.