Question

is there any natural number having no factor at all​

Answer 1

The number with the fewest factors would be 1 as it is only divisible by itself. ... No Natural Numbers have no factors. The minimum is one and there is no maximum. One may posit that 0 has none (even thought it is not a natural number) but it is actually divisible by all numbers as anything can fit evenly 0 times into 0.