Shares of Apple were nearly unchanged in early trading after the stock last week repeatedly hit record highs in anticipation of the iPad's launch on Saturday.
The company said first-day sales included deliveries of preordered iPads to customers, deliveries to channel partners and sales at Apple Retail Stores.
A number of U.S. stores were closed for the Easter holiday on Sunday, but some did remain open, which suggests that total weekend figures will be higher.
Several analysts had expected the company to sell 250,000 to 350,000 units on the opening weekend.
The big question is whether brisk sales are sustainable, or whether last weekend's crowds consisted primarily of hardcore Apple fans and early adopters.
At the moment, Wall Street analysts expect iPad sales to reach about 5 million units in the first 12 months.
At least four brokerages raised their share-price targets and full-year earnings estimates for Apple following the debut of the highly anticipated mobile touchscreen computer that lets users watch video, read newspapers and search the Web.
For the weekend, Kaufman Brothers analyst Shaw Wu expected sales of 250,000 to 300,000 units. Barclays Capital analyst Ben Reitzes estimated that Apple sold about 400,000 iPads.
Companies found to have supplied some of the key components to the iPad received a boost in trade on Monday [ID:nN03146377].
Those include Samsung Electronics, up 1.5 percent, LG Display, up 2.2 percent, Broadcom Corp up 2.0 percent, and Texas Instruments Inc, up 1.1 percent.
JPMorgan analyst Mark Moskowitz said critical mass depended on future product generations overcoming current limitations.
In the interim ... Apple faithful and the early adopters should help the iPad beat subdued investor expectations, he said in a note to clients.
Susquehanna Financial analyst Jeffrey Fidacaro, who expects a smaller second wave of demand in late April for the 3G version, said the iPad was likely to take share from Amazon.com Inc's Kindle because of its robust e-reader capabilities.
Apple has plenty riding on the iPad, which it unveiled in January and calls a new category of machine: a lightweight media consumption device that tries to fuse the best attributes of a smartphone and a laptop.
JPMorgan raised its price target on Apple stock to $305 from $240; Kaufman Brothers increased it to $295 from $253; and Thomas Weisel Partners lifted its price target to $280 from $270. Susquehanna raised its price target to $275 from $260, while Barclays kept its unchanged at $285.
Shares of Apple were down less than 0.1 percent at $235.78 in morning trading.
Apple added that iPad users had downloaded more than 1 million applications from the company's App Store and more than 250,000 ebooks from its iBookstore during the first day.
(Reporting by Franklin Paul in New York and Supantha Mukherjee in Bangalore; Editing by Saumyadeb Chakrabarty and Lisa Von Ahn)