11
4, 9, 25, 49
6 (1,2,3,6) 10 (1,2,5,10) and 15 (1,3,5,15).
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.
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.
there are 3 no.2,3 & 5
14 (I think).
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
Nothing special. They are squares of prime numbers.