Sūrah No.114. Revealed in Makkah, 6 verses.
Both Sūrat al-Falaq and Sūrat al-Nas seek refuge in Allah, but al-Falaq asks for protection from all forms of evil, while al-Nās focuses on protection from the evil effect of whisperings on the soul.
Some narrators say that Sūrat al-Falaq and Sūrat al-Nās were revealed together.