[tex] {3}^{7} = 3 \times 3 \times 3 \times 3 \times 3 \times 3 \times 3[/tex]
[tex] = 2187[/tex]
[tex]3 {}^{21} = (3 {}^{7} ) {}^{3} = 2187 {}^{3} [/tex]
[tex]10000 > 2187[/tex]
