I'm going to estimate that he's been with between 15 and 40. It's hard to tell since he's been so tight-lipped about his past.
My father was born in the late 50s. He hasn't said anything about his early sex life except the fact that he was too drowned in homework during his primary school years at a boarding school to care for girls. After that, he went to an Ivy and I'm sure got laid a few times given that he was in business, lifted weights, and lived in the city. After that, I know he got laid a bit since he usually tried to find an acquaintance when he traveled abroad. He traveled quite a bit(probably 30 - 50 nations cumulatively in his 20s) and worked in the Middle East for a couple years as well. His only release was when he traveled out of the desert during that time on cheap flights for short vacations. Probably a p4p guy since he was making the equivalent of a six-figure income right out of college and was more of a business-smart book nerd than a player. Either that or he was attracting foreign gold diggers. I know for a fact he got some in Thailand(before it was cool) and Kenya.
He ended up meeting my mother in grad school, married, had me, and then divorced a few years later. Since then, his life has been a death spiral and at this point, unless he's been paying for hookers or living a second life, he's probably a veteran incel.