9
9 The three factors are 1, 3, and 9. 9 The three factors are 1, 3, and 9.
26
Factors of the number will also be factors of the number's multiples. Multiples of the number will also be multiples of the number's factors.
the next number will be 2 3 4 3 4 2 2 .............
the answer is 3
Three is prime, because the number 3 only has 2 factors 1 and itself and the number 4 has 3 factors 1,2, and 4 (you can tell if a number is prime when it has 2 factors and if a number has more than 2 it is composite)
4
4
6
There is no such number. Any prime number raised to the third power has exactly four factors. For example, 23 = 8; its factors are 1, 2, 4, 8 (1, 2, 22, 23). Since - as is well-known - there is no largest prime number, there is no largest number that has exactly four factors.
The next number in the sequence is 18. It's +1, +2, +3, +4, ....
It is: 25 that is the next square number