Learn Spanish (Latin America): Hay dieciséis perros y diecisiete gatos aquí. - There are sixteen dogs and seventeen cats here.

In modern Spanish, numbers 16 through 29 are written as a single word. For the teens, the older phrase diez y seis (ten and six) gets squished together. When this happens, the z turns into a c, and the y becomes an i, creating dieciséis.

Why does dieciséis have an accent mark while diecisiete doesn't?

When diez y seis becomes one word, Spanish pronunciation rules would normally shift where the vocal stress lands. We add an accent mark to dieciséis to force the stress to stay on the final syllable. For diecisiete, the natural stress already lands on the correct syllable, so no accent mark is needed.

Doesn't hay usually mean 'there is'?

The word hay is a great multitasker: it means both 'there is' and 'there are'. You don't have to change it at all when you go from talking about a single item to plural items like dieciséis perros.

Do numbers like diecisiete change if I'm counting feminine objects instead of masculine ones?