Even the iPhone can't save Apple

Apple (AAPL) did it! It sold 13 million new iPhones in the first weekend - beating expectations and sales numbers from the launch of the last version of the phone.

But even these numbers aren't enough to impress investors. And there's a good reason why.

Shares of Apple are down $1.41, or 1.3%, to $113.25 Monday as investors react to the weekend sales statistics of the new iPhone. Bulls were hoping strong sales of Apple's latest smartphone model would be the catalyst to get the stock working again. Guess not - partially because the numbers aren't as solid as they sound.

Certainly, the market is down, too. The S&P 500 is off even more, 1.7%, as investors readjust their valuations. But that's kind of the point. Apple's product cycle is supposed to be what makes the company - and stock - immune from the vagaries of the rest of the market.

On its face, Apple's news looks solid. Apple says it sold 13 million units of the new iPhone 6S to its faithful consumers, beating the 10 million launch sales of the iPhone 6 in 2014, says Nomura analyst Jeffrey Kvaal.

But there's the problem. The number is a bit distorted because this year 12 global regions including China were included in launch, versus 10 last year, says Abhey Lamba of Mizuho. China wasn't included at launch last year.

Seeing the shares fall following the seemingly better-than-expected smartphone sales is a disappointment for the legions of investors bullish on Apple. Many looking for some good news - anything - to get the stock moving higher again. Shares of Apple are down 15.9% from their high this year - an even worse showing that the market. The Standard & Poor's 500 is down 11.1% from its high.

The iPhone weekend sales numbers underscore - too - how Apple's reliance on an aging product line for a majority of its profit is tricky as the smartphone market matures. While consumers may eventually upgrade their devices, many will delay the upgrade until they need to be replaced. It's similar to the maturation that has occurred in the personal computer market.

The number exceeded many analysts' estimates, including a 12 million forecast from S&P Capital IQ's Angela Zino. Timing will also help Apple as many of the launch weekend sales will fall into the fourth quarter this year, versus the third quarter of last year, Lamba says. Plus, Apple plans to ship new phones to 130 countries, up from 115 last year.

Analysts remain hugely bullish on Apple stock. The average 18-month price target is $146.76. Lamba, though, is much more cautious saying the stock's target is $125.

"We continue to like the company and its strong franchise but not that it is primarily a smartphone company, which could make it tough for the stock to work in light of tough compares," Mizuho says.