30, 42, 66, 78, 102, 105, 114, 138 all have exactly three distinct prime factors.
We don't generally consider the negative factors of positive numbers, but they are exactly the same digits as the positive factors, just with minus signs.
Of the numbers from 1 to 30, only 30 has all three of those numbers as factors.
There are not common factors of 30 because there cannot be common factors without two or more numbers to compare. Common factors are factors that the numbers being compared have in common. The factors of 30 are 1, 2, 3, 5, 6, 10, 15, and 30. The prime factors of 30 are 2, 3, and 5.
The common factors of 30 and 300 are the numbers that can divide both 30 and 300 without leaving a remainder. The factors of 30 are 1, 2, 3, 5, 6, 10, 15, and 30. The factors of 300 are 1, 2, 3, 4, 5, 6, 10, 12, 15, 20, 25, 30, 50, 60, 75, 100, 150, and 300. Therefore, the common factors of 30 and 300 are 1, 2, 3, 5, 6, 10, 15, and 30.
Numbers with three factors are squares of primes. So: 4, 9, 25
Prime numbers have exactly two factors. 53 and 59 are prime numbers.
The prime numbers between 30 and 50 are 31, 37, 42, 43 and 47.
31 37 47
There are an infinite number of them. 8 has three prime factors, 30 is the first with three distinct prime factors.
30, 42, 66, 78, 102, 105, 114, 138 all have exactly three distinct prime factors.
The numbers between 10 and 30 that have exactly 5 factors are 16 and 25. The number 16 has factors 1, 2, 4, 8, and 16. The number 25 has factors 1, 5, 25, but since it is a perfect square, it also includes the repeated factor of 5. These are the only two numbers between 10 and 30 that have exactly 5 factors.
30, 42, 66, 70 and 78.
The factors of 30 that are not prime numbers are 6, 10 and 30.
We don't generally consider the negative factors of positive numbers, but they are exactly the same digits as the positive factors, just with minus signs.
There are five of them: 31 37 41 43 47
Of the numbers from 1 to 30, only 30 has all three of those numbers as factors.