9 = 1, 3, 9
4 = 1, 2, 4
9
20 25
2,3
S
91
4
424
11
4, 9, 25, 49
The numbers less than 100 with exactly 6 factors are of the form a2b where a and b are different primes. 12, 18, 20, 28, 44, 45, 50, 52, 63, 68, 75, 76, 92 and 99.
6 (1,2,3,6) 10 (1,2,5,10) and 15 (1,3,5,15).
There are 31 numbers less than 1,000 which have an odd number of factors. They are: 1,4,9,16,25,36,49,64,81,100,121,144,169,196,225,256,289,324,361,400,441,484,529,576,625,676,729,784,841,900,961.
By definition, a prime number has exactly two factors. So, there are no prime numbers with exactly three factors.
Four numbers less than thirty, 12, 18, 20, and 28, each have exactly 6 factors.
4, 9, 25 and 49 They are squares of prime numbers.
11
Just 36.
14 (I think).
there are 3 no.2,3 & 5
1, 2, 3, 5, and 7
Every prime number has exactly two factors. They are '1' and the number itself. There are 15 prime numbers less than 50. A few of them are 2, 3, 5, 7, 11, 13, and 47.
4, 9, 25, and 49
4, 9, 25, 49
prime squares 4, 9, 25, 49