diecisiete
/djeθiˈsjete/ · B2 · num
seventeen
diecisiete = diez (ten) + y + siete (seven): 10 + 7 = 17
Spanish builds 16 to 19 from diez plus siete-style parts. Diecisiete fuses diez (ten) with siete (seven), so it is literally ten-and-seven. The same pattern gives dieciséis, dieciocho and diecinueve.