CREATE TABLE table_21210 ("No." FLOAT, "Hanyu" TEXT, "Tongyong" TEXT, "Pe\\u030dh-\\u014de-j\\u012b" TEXT, "Chinese" TEXT, "Area  ( km\\u00b2 ) " TEXT, "No. of villages" FLOAT, "Population  ( 2010 ) " FLOAT)

Name the number where population 2010 is 171906
SELECT "No." FROM table_21210 WHERE "Population (2010)" = '171906'
SELECT "No." FROM "table_21210" WHERE "Population (2010)" = '171906'