5x5x5x5x5x5

5*5*5*5*5*5 = 5^6 = 5^3 * 5^3 =125 *125 = 15625//

1234554321 * 30%

= 3703662963000//

$$\underset{\,\,\,\,{\textcolor[rgb]{0.66,0.66,0.66}{\rightarrow {\mathtt{easily, calculated, if, you, change, it, from, percentage, form, to, decimal}}}}}{{solve}}{\left(\begin{array}{l}{\mathtt{5}}{\mathtt{\,\times\,}}{\mathtt{5}}{\mathtt{\,\times\,}}{\mathtt{x5}}{\mathtt{\,\times\,}}{\mathtt{5}}{\mathtt{\,\times\,}}{\mathtt{x5}}{\mathtt{\,\times\,}}{\mathtt{5}} = {{\mathtt{5}}}^{{\mathtt{6}}}={\mathtt{15\,625}}\\ {\mathtt{0}}\%={\mathtt{0}}\\ {\mathtt{of}}={\mathtt{0}}\\ {\mathtt{1\,234\,554\,321}}={\mathtt{0}}\\ {\mathtt{3}}{\mathtt{\,\times\,}}{\mathtt{1\,234\,554\,321}}={\mathtt{370\,366\,296}}\\ {\mathtt{3}}={\mathtt{0}}\end{array}\right)}$$