How many three-digit numbers can be expressed as an integral power of 2?<br/>

We need three-digit powers of 2. 2^6 = 64, 2^7 = 128, 2^8 = 256, 2^9 = 512, 2^10 = 1024. So the three-digit ones are 128, 256 and 512. Total = 3.