Does the integer k have at least three different positive prime factors?(1)k/15 is an integer(2)k/10 is an integer答案写（1）中15的positive prime factors 是3 跟5 我想问下为什么没有1呢?1不属于prime factor吗?

Does the integer k have at least three different positive prime factors?(1)k/15 is an integer(2)k/10 is an integer答案写（1）中15的positive prime factors 是3 跟5 我想问下为什么没有1呢?1不属于prime factor吗?
Does the integer k have at least three different positive prime factors?
(1)k/15 is an integer
(2)k/10 is an integer
答案写（1）中15的positive prime factors 是3 跟5 我想问下为什么没有1呢?1不属于prime factor吗?

Does the integer k have at least three different positive prime factors?(1)k/15 is an integer(2)k/10 is an integer答案写（1）中15的positive prime factors 是3 跟5 我想问下为什么没有1呢?1不属于prime factor吗?
1 既不是质数也不是合数,很特殊的一个数~