find digits if u can

$log 5 = log \frac{10}{2} = log 10 - log 2 = 1- 0.3010 = 0.6990$

$log 5^{20} = 20 log 5 = 20 \times 0.6990 = 13.98$

5^20 = 25^10, 10^(x-1) = 25^10, x-1 = log (25^10) = 10 x log25 = 13.9, hence x = 14.9, and we run down to 14

Its very easy by logic.... Till 5^4 the number of digits are only 3 but after that the digits add up by 1... So we can predict the number of digits might be 20-4 =16