This depends on the individual. Atheism only means that someone doesn't believe in god or gods. It doesn't really carry a code of conduct with it.
Some people are very uncomfortable having sex with someone that they don't share an emotional tie. Other people can have sex with no emotional attachment at all. Both individuals can be good, honest people who care about others. Number of sexual partners says nothing about an individual's ability to show empathy or be honest. It doesn't say how well they will do their job or if they will be good parents or anything else.
As long as the individual doesn't lie to get someone in bed, sleeps only with consensual partners, and doesn't break their word, I don't care how many or how few sexual partners that they have had. For me, it is a non-issue but I don't speak for all atheists.
Some people are very uncomfortable having sex with someone that they don't share an emotional tie. Other people can have sex with no emotional attachment at all. Both individuals can be good, honest people who care about others. Number of sexual partners says nothing about an individual's ability to show empathy or be honest. It doesn't say how well they will do their job or if they will be good parents or anything else.
As long as the individual doesn't lie to get someone in bed, sleeps only with consensual partners, and doesn't break their word, I don't care how many or how few sexual partners that they have had. For me, it is a non-issue but I don't speak for all atheists.