Since $128=2^{7}$, its positive divisors are $2^{0}=1, 2^{1}=2, 2^{2}=4, 2^{3}=8, 2^{4}=16, 2^{5}=32, 2^{6}=64, 2^{7}=128$. Of these, the integers $1,4,16,64$ are perfect squares, which means that 128 has three positive divisors that are perfect squares larger than 1.