In a large population, very close to 25% of the observations will fall below the 25th percentile (Q1), and close to 75% fall below the 75th percentile (Q3). The Web site of the Educational Testing Service reports that on the SAT Verbal test, with a possible perfect score of 800, the 87th percentile of 1,475,623 scores nationwide is a score of 640. What is the best estimate of exactly how many scores were below 640?