ans is 25 and the prime numbers are
1.2(two)
2.3(three)
3.5(five)
4.7(seven)
5.11(eleven)
6.13(thirteen)
7.17(seventeen)
8.19(nineteen)
9.23(twenty three)
10.29(twenty nine)
11.31(thirty one)
12.37(thirty seven)
13.41(forty one)
14.43forty three)
15.47forty seven)
16.53(fifty three)
17.59(fifty nine)
18.61(sixty one)
19.67(sixty seven)
20.71(seventy one)
21.73(seventy three)
22.79(seventy nine)
23.83(eighty three)
24.89(eighty nine)
25.97(ninety seven)
PS:1 is not a prime number