Question

Which of the following numbers has the largest number of unique prime factors?: {78, 217, 74, 420}

Answer 1

`420` has the largest number of unique prime factors.

Explanation:

Prime factors of `78` are `2`, `3` and `13` as `78=2xx3xx13`

Prime factors of `217` are `7` and `31` as `217=7xx31`

Prime factors of `74` are `2` and `37` as `74=2xx37`

Prime factors of `420` are `2`, `3`, `5` and `7` as `420=2xx2xx3xx5xx7`

Hence, `420` has the largest number of unique prime factors.