9
9 The three factors are 1, 3, and 9. 9 The three factors are 1, 3, and 9.
26
the next number will be 2 3 4 3 4 2 2 .............
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 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
The next number in the sequence is 18. It's +1, +2, +3, +4, ....
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 series 2-4-3-9-4 is 16. 2 squared is 4, 3 squared is 9, 4 squared is 16