Question 165
Find all the positive integers $\overline{abcd}$ knowing that the following conditions hold:
a) $a^2 + b^2 + c^2 + d^2$ is divisible by $4$;
b) the remainder of $\overline{abcd}$ when divided by $c$ is $7$.
a) $a^2 + b^2 + c^2 + d^2$ is divisible by $4$;
b) the remainder of $\overline{abcd}$ when divided by $c$ is $7$.