For $0.007\text{ m}^2$, the leading zeros are not significant; only '7' is significant (1 significant figure). For $2.64 \times 10^{24}\text{ kg}$, the exponential term does not contribute to the significant figures; only '2', '6', and '4' are significant (3 significant figures). For $0.2370\text{ g cm}^{-3}$, the trailing zero after the decimal point is significant, meaning '2', '3', '7', and '0' are all significant (4 significant figures).