That's an infinite list. Numbers with three factors are the squares of prime numbers.
3, 6, 9, 12, 15 and just keep adding three until you get to infinity.
All prime squares have just three factors. Example: 9, 25
Squares of prime numbers
Of the numbers from 1 to 30, only 30 has all three of those numbers as factors.
That depends what number you are trying to find the factors of - all those three numbers are factors of the number 18.
Prime numbers have two factors. Prime squares have three factors. Square numbers have an odd number of factors but that number varies.
Prime numbers have two factors. 2, 3 and 5 are prime numbers.
There are no common factors for all three numbers.
Factors don't have numbers. Numbers have factors. Numbers that have the factors 2, 4 and 8 are 8 and all of its multiples.
Of the numbers from 1 to 30, only 30 has all three of those numbers as factors.
Squares of prime numbers have only three factors.
Calculate the least common multiple of the three numbers. Any multiple of that has all those numbers as factors.
They don't. 21 has two prime factors. 42 has three prime factors.
The only factors common to all three numbers are... 1 & 5
By definition, a prime number has exactly two factors. So, there are no prime numbers with exactly three factors.
That depends what number you are trying to find the factors of - all those three numbers are factors of the number 18.
Composite numbers
Numbers with exactly three factors are squares of prime numbers.
The numbers with only three factors are squares of prime numbers.
Squares of prime numbers have exactly three factors.