Which square number below 100 also prime numbers?

There's no this kind of number because when a number is a square number, it equals its square root multiplies itself, which contradicts with the definition of prime number (A prime number is a natural number greater than 1 that has no positive divisors other than 1 and itself). There's only 1=1×1, but since 1 isn't included in prime number, there's no answer to your question.