Are you that simple?
ok, let's look at the naive picture. AAPL has about 24.5B in cash and short-term investments as of end of last quarter. That's telling you nothing yet, since the company also has other current and non-current assets, and you have to subtract liabilities. Let's say current assets minus current liabilities (net tangible assets include non-liquid ones and various accounting issues in this market), that's about 18.5B. No sane company would use that completely for acquisitions, today's lending markets being what they are. But still. Now, Nokia has a market cap of some 49B and you bet any hostile takeover[*] would require quite a premium to convince shareholders, plus investment banking fees. Putting that at a 40% extra is very conservative, but let's assume that. You end up with some 70B acquisition costs. So AAPL would have to raise roughly Nokia's market cap beyond their net current assets, which is slightly less than a third of their market cap. Apple's stock would tank if they tried to raise that kind of money, either in the stock market or via bonds, making it even harder to do.
So no, Apple can't buy Nokia.
[1] management is free to refuse a takeover offer. Then, if enough shareholders disagree, they can hold a shareholder meeting, boot management and go ahead with the sale. Then, you have regulators to convince to approve the sale, particularly for such large companies. So it's not that simple even with a public company. Just ask Larry, Oracle has been playing this game a lot lately.