what are the 5 smallest integers that are a multible of 90, and are a perfect power of 6?
I don't quite understand your question! ALL multiples of 90 end in zero and ALL powers of 6 end up in 6 and are not divisible by 90. Example: 990 is a multiple of 90 but cannot be expressed as "perfect power of 6", in the sense that there such number n, where 6^n =990. If that is what you mean ! If you mean that the multiples of 90 that are also multiples of 6, then that is a different thing altogether.