Question: What other country does the most populated nation in the world share a border with and how long is the border between the two nations?
SQL: SELECT T2.Country2, T2.Length FROM country AS T1 INNER JOIN borders AS T2 ON T1.Code = T2.Country1 INNER JOIN country AS T3 ON T3.Code = T2.Country2 WHERE T1.Name = ( SELECT Name FROM country ORDER BY Population DESC LIMIT 1 )