65
33
17
It is 129.
Think it's 30...then 20
29
65
17 cause it is the next prime number
33
Big numbers can be difficult to factor. You know 2 isn't a factor because it's not an even number. You know 3 isn't a factor because the sum of digits 2+4+5+3 = 14 is not a multiple of 3. You know 5 isn't, either, because it doesn't end in 5 or 0. Next try 7 - also not a factor. The next prime to try is 11: 2453 = 11 * 223 Now we're getting somewhere. Is 223 prime? The next factor to test for is 13. It is not a factor of 223. We can quit now because the next prime is 17, and 17^2 > 223. So 223 is prime. So the answer is simply 2453 = 11 * 223
33
28 (add on the prime number 11)
143
14
17 is a prime number - the next composite number after 17 is 18.
17
17