The given number series is
3, 5, 8, 15, 28, 51, ?
Here the pattern it follows is
3
3 + 2 = 5 ( add prime number less than 3 i.e, 2)
5 + 3 = 8 (3 is prime number less than 5)
8 + 7 = 15 (7 is prime number less than 8)
15 + 13 = 28 (13 is prime number less than 15)
28 + 23 = 51 (23 is prime number less than 28)
51 + 47 = 98 (47 is prime number less than 51)
Hence, the next number in the given number series is 98.
