According to the search results, the estimated population of Vatican City in 2023 varies depending on the source. Here are the different estimates:

• World Population Review: 518
• Wikipedia: 764
• Population Today: 520
• Worldometer: 520
• Population.city: 873 (if the growth rate from 2011-2014 continued)

Its important to note that the estimates from different sources may vary due to different methods of data collection and calculation. However, based on the available information, the most commonly cited estimate is around 520-764 residents in Vatican City in 2023.