The average of 5 consecutive numbers is 21. The highest number will be?

The average of five consecutive numbers is 21.

If the average of five consecutive numbers is 21, then 21 is the middle (third) number in this sequence. The numbers are equally spaced by 1 units (since they are consecutive odd numbers).

As consecutive number series average number is also middle number of the series.

So, series is;

19, 20, 21, 22, 23

Thus, The largest number out of these five numbers is 23
Alternate Solution:​
Let the numbers be x, x + 1, x + 2, x + 3, x + 4.
​$$\text{Average} = \frac{x + (x + 1) + (x + 2) + (x + 3) + (x + 4)}{5} \\\Rightarrow 21 = \frac{5x + 10}{5}$$​​
=> 105 = 5x + 10
=> 95 = 5x
=> x = 19
Highest number = x + 4
=> 19 + 4
=> 23.