[tex]961 = 31^2 \\
b=(5^{62}+5^{61}+5^{60}) \times 961 = \\
= 5^{60}(5^2+5^1+5^0) \times 31^2 = \\
= 5^{20 \times 3}(25+5+1) \times 31^2 = \\
= (5^{20})^3 \times 31 \times 31^2 = \\
=(5^{20})^3 \times 31^3 = \\
= \boxed{(5^{20} \times 31)^3 = cub~perfect }[/tex]
