Fifty-five million. That's the number of iPhones analysts believe, on average, that Apple (NASDAQ:AAPL) sold in its first quarter of 2014. That many iPhones sold would mark Apple's best quarterly smartphone sales ever.

Let's explore the implications: What would 55 million iPhones mean for Apple? And what's driving its robust iPhone sales?

Looking at the numbers
Estimating Apple's iPhone sales is easier than it used to be. After Apple adjusted the way it provides guidance to a much more realistic (and accurate) method, analysts' consensus estimates have been closer to actual results. So, assuming these estimates are, indeed, fairly close to what Apple will report when it provides first-quarter results on Monday, how will 55 million iPhones affect Apple's results?

Assuming the average selling price remains the same as last quarter, the iPhone segment could account for about $32 billion of Apple's revenue. Based on analyst estimates of $57.9 billion in total revenue for the quarter, therefore, the iPhone could account for about 55% of Apple's top line -- slightly below the 56% of revenue the segment accounted for in the year-ago quarter.

With iPhone sales equally as important to results and unit estimates for the quarter's sales 15% higher than the year-ago figure, the iPhone may contribute more to Apple's bottom line than ever before. No wonder analysts, on average, are estimating record EPS at $14.32. Though $14.32 in EPS is only 3.7% higher than the year-ago quarter, the gain on the bottom line will be Apple's first in four quarters.

Where is all this growth coming from?
Given all the negative Apple headlines highlighting its dwindling global market share, it would be easy to assume that the company isn't growing any more. But that's just not the case. So how is Apple still growing despite intensifying competition? The growth can be explained in two points.

1. Apple's gaining market share in the United States. In the U.S., Apple's largest market, Apple is doing extremely well. In fact, iPhone ownership in the U.S. is up seven percentage points in the fourth quarter of 2013 from the year-ago quarter, according to NPD. 

2. Apple is benefiting from overall smartphone market growth. Despite Apple's dwindling market share abroad as lower-cost Android devices make outsized gains in market share in many markets, Apple is still benefiting from the market's overall growth.

Is this the beginning of more growth for Apple?
With analysts predicting growth in Apple's earnings per share on the strength of record iPhone sales, can investors expect more growth from Apple in the future?

It's definitely possible. There's likely still plenty of growth ahead for Apple's iPhone and iPad segments. IDC pegs its estimates for annualized growth in smartphone and tablet shipments between 2013 and 2017 at about 15%. Indeed, the average analyst estimate on Yahoo! Finance for Apple's EPS growth next year is 10%. Looking out over the next five years, the outlook is even more bullish: Analysts expect EPS growth of about 15% per annum.

If Apple is selling record iPhones, reporting record revenue, and growing its bottom line, does a conservative valuation of 13.8 times earnings make sense?

What do you think? Will Apple sell 55 million iPhones in Q1?