How many digits are there in the number N =213 ⋅59N = 2^{13} · 5^9N =213 ⋅59? Solution N =213 ⋅59 =24 ⋅29 ⋅59 =24 ⋅109 =16⋅109 =1.6⋅1010,N = 2^{13} · 5^9 = 2^4 · 2^9 · 5^9 = 2^4 · 10^9 = 16 · 10^9 = 1.6 \cdot 10^{10},N =213 ⋅59 =24 ⋅29 ⋅59 =24 ⋅109 =16⋅109 =1.6⋅1010, which has 111111 digits.