The number 512, in large and bold print, almost leaped from an advertisement in this newspaper a few days ago. Smaller print in the ad went on to explain that this was the number of accused shoplifters arrested in the Washington metropolitan area during the seven-day period that ended last Sunday.

Such ads will continue through the upcoming holiday shopping season as part of the Greater Washington Board of Trade's annual anticrime campaign, which emphasizes the fight against that form of thievery.

As part of its campaign, the business group has assembled some fascinating statistics. For instance: The single largest class of offenders is housewives (25 percent), followed by male teen-agers (13 percent) and female teen-agers (12 percent). Older teen-agers, ages 17 and 18, are most frequently arrested. Female white-collar workers account for 9 percent and male white-collar workers for 5 percent. So-called professional thieves account for 6 percent of arrests. In grocery stores, 55 percent of all shoplifters are housewives. When it comes to passing bad checks, female white-collar workers top the list with 24 percent, followed by housewives with 22 percent. A majority of bad-check writers, 56 percent, are in the middle-income group.