Find the Odd one out of the given series

6, 15, 35, 77, 165, 221

Here the given series is 1, 3, 6, 11, 20, 37, ??,

and the logic behind the series is

1 x 2 + 1 = 3

3 x 2 + 0 = 6

6 x 2 + (-1) = 11

11 x 2 + (-2) = 20

20 x 2 + (-3) = 37

37 x 2 + (-4) = 70

Hence, the next number in the given series is 70.

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.

The given number series 2676, 445, ?, 21,6, 2, 1 follows a pattern that,

From right side,

1

1 x 1 + 1 = 2

2 x 2 + 2 = 6

6 x 3 + 3 = 21

21 x 4 + 4 = 88

88 x 5 + 5 = 445

445 x 6 + 6 = 2676

Hence the missing number in the given number series is 88.

The given number series 2, 19, 0, 21, –2, ? follows a pattern,

2

2 + 17 = 19

19 - 19 = 0

0 + 21 = 21

21 - 23 = -2

-2 + 25 = 23

Hence, the next number in the series is 23.

Here the given number series  3, 10.5, 36.75, 128.625, ? follows a pattern that

3

3 x 3.5 = 10.5

10.5 x 3.5 = 36.75

36.75 x 3.5 = 128.625

128.625 x 3.5 = 450.187

Hence the next number in the given number series is 450.187.

The given number series is 125,   138,   164,   ?,   255

125

125 + 13x1 = 138

138 + 13x2 = 164

164 + 13x3 = 203

203 + 13x4 = 255

Hence, the missing number in the series is 203.

Here the given number series is 5  11  21  44  ?  175

Now the given series follows a pattern, that

x2 + 1, x2 - 1, x2 + 2, x2 - 2, x2 + 3, x2 - 3,...

Then the missing number is x2 - 2

= 44 x 2 - 2 = 88 - 2 = 86

Hence, the missing number in the number series is 86.

Here among the given numbers, 3, 19, 67 are prime numbers. And 133 is not a prime number.

Hence, the odd number of the given numbers is 133.