Question

How many three digit numbers have exactly three factors?(including 1 and itself)

Answer 1

There are seven numbers in total.These are

121, 169, 289,361, 529, 841 and 961

Answer 2

For a 3-digit number to have exactly three factors then it must be square of a prime number.or we can say that For a number, N, to have exactly three factors, its prime factorization must be of the type p² where p is a prime number.

p=11, 13, 17, 19, 23, 29 and 31 

so that the prime factors will be 1; the prime no. that the no.,n, is square of and the no. itself

and the no.s are:

1) 121= 1,11,121

2)169= 1,13,169

3) 289= 1,17,289

4) 361= 1,19,361

5) 529= 1,23,529 

6) 841= 1,29,841

7) 961= 1,31,961

HOPE THAT HELPS

REGARDS