The nation's factories operated at only 74.9 percent of their capacity last month, a sharp drop from the 76.9 percent capacity utilization in October, the Federal Reserve Board reported yesterday.

Meanwhile, personal incomes rose by only 0.6 percent during the month, a separate report from the Commerce Department showed. Price rises during the month probably offset most, if not all, of the income increase. Higher taxes meant that there was only a 0.5 percent increase in disposable personal income available for spending.

However, people apparently saved less in order to keep up spending. The report showed a 1 percent rise in personal consumer spending during November. But yesterday's figures suggested that the saving rate, which has risen in recent months, stayed close in November to the 5.9 percent rate recorded in October.

With the evidence of recession building, Commerce Secretary Malcolm Baldrige said yesterday that he expects the early "flash" numbers to show a fall of 5 percent or more in gross national product during the final quarter of this year. Earlier this week, other administration economists were reported as predicting a fall of 6 or 7 percent in GNP, a measure of the nation's output of goods and services.

Baldrige told reporters that if the fourth-quarter figure for the GNP is better than he expects, it just would make him worry about the prospects for the early months of 1982. He said that there would probably be negative growth for the first half, with positive growth of 5 percent or more in the second half.

Despite the economic slump, interest rates apparently have stopped sliding this week, although some analysts expect further falls in coming weeks. Fears of large federal deficits have pushed some short-term interest rates back up, and some market participants believe that the Federal Reserve Board does not want rates to fall too swiftly. Yesterday, Continental Illinois Bank of Chicago moved its prime rate back up to 15 3/4 percent, the ruling prime rate level, from 15 1/2 percent.

In other economic news yesterday, the Commerce Department reported that the U.S. balance of payments current account was in surplus by $2.1 billion in the third quarter of this year. This measure includes all exports and imports of goods and services, as well as international financial transactions.

The surplus on the current account in July, August and September was bigger than the $1.14 billion recorded in the second quarter. However the merchandise trade balance stayed firmly in deficit in the period.

The Commerce Department reported that "a $1.5 billion increase in net service receipts to $11 billion more than accounted for the increase" in the overall current account surplus.

Officials expect that the current account may slip into deficit next year, as the stronger dollar slows exports and boosts imports, and the projected economic recovery in 1982 brings in more imports.

The Federal Reserve report showed that while all manufacturing industry is cutting output in response to the recession, the auto industry is hit hardest. Its capacity utilization slumped to 50 percent in November from 58.2 percent in September and 55 percent in October.