Here's a quick review of how numbers 1-100 work in Spanish.

• From 1 to 15, you just have to memorize each one: uno, dos, tres, etc.
• From 16 to 19, we are just saying 'ten and six', ''ten and seven', etc. but as a single word: dieciséis, diecisiete, etc.
• Then you need to memorize all the multiples of 10: veinte, treinta, cuarenta, etc.
• From 21 to 29 we again say 'twenty and one', 'twenty and two', etc. but as a single word, and we drop the 'e' in 'veinte': veintiuno, veintidós, etc.
• From 31 on, it gets easier: we just say literally 'thirty and one', 'thirty and two', etc. and same thing after 40, 50, etc: Treinta y uno, treinta y dos, cuarenta y uno, cuarenta y dos, etc.

Here's a video of Dan pronouncing all of them (using both central/northern Spanish and southern Spanish/Latin American pronunciation: