For an octave band, centre frequency is the geometric mean of the lower and upper frequencies:
\[
f_c = \sqrt{f_1 f_2}
\]
\[
f_c = \sqrt{710 \times 1420} = \sqrt{1008200}
\]
\[
f_c \approx 1004.09
\]
Rounded to nearest integer:
\[
\boxed{1004\ \text{Hz}}
\]