I wear size womens 20. What size should I get in this jacket?

I would suggest a size 4X because these jackets run very small. I wear a size XL in men’s t shirts and a size XXL in women’s t shirts. I got a size 4X in this Levi jean jacket and it is perfect for me. Enough room to fit loose over my clothes.

Can men wear this jacket?

Absolutely ! My husband found it here and couldn't believe the price of $25.00. He bought it when it arrived compared it to his other Levi's jackets and said "yep that'll work". He wished he'd bought atleast 2 because they are listed at around $89.00. Purchased item sku was "Sweet Jane (waterless) , when it arrived we couldn't believe that it was a dark indigo non treated original Levi Trucker Denim Jacket. Looked just like his 30 yr old ones without all the wear and tear.