State Highway 21 runs from Chalakudi
on the National Highway 47
up to Anamalai
, on the Kerala
border, in Thrissur District
. State Highway 21 starts at Chalakudi and runs eastwards touching Athirampally, Vazhachal, Peringalkuthu and through the approach road to Sholayar Power House, before ending at Anamalai. State Highway 21 has a total length of 86 km.