It is usually challenging to find growth stocks trading at affordable valuation multiples. That's because growth stocks command a premium when compared to average stocks, thanks to the rapid pace of increase in their top and bottom lines, which outpaces the overall industry or the business they operate in.

However, some growth stocks are terrific bargains right now, like Apple (NASDAQ:AAPL), Chewy (NYSE:CHWY), and Micron Technology (NASDAQ:MU). Investors can buy them right away as they trade at relatively attractive valuations, and they seem capable of sustaining their impressive momentum for a long time to come thanks to a bunch of secular catalysts. Let's take a closer look at these three screaming buys right now.

1. Apple

Apple has stepped on the gas after the launch of its 5G-enabled iPhone 12 models. The company's revenue in the first six months of fiscal 2021 has shot up 34% year over year to $201 billion, a huge jump over the 5.5% top-line growth it registered in fiscal 2020 which ended in September last year.

Person pressing Buy button on a keyboard.

Image source: Getty Images.

The iPhone 12 lineup dominates the 5G smartphone market, cornering more than 30% of shipments in the first quarter of 2021. Apple shipped 40.4 million 5G iPhones in the first quarter of the year, nearly double the shipments of second-place Oppo as per Strategy Analytics.

The iPhone maker's 5G dominance pushed its overall smartphone shipments to 57 million units in Q1, up 44% over the prior-year period. It is worth noting that Apple's growth was significantly higher than the overall smartphone market's year-over-year growth of 24% during the quarter. This helped it close the gap with first-place Samsung, which registered a 32% year-over-year increase. Apple's average selling price (ASP) per iPhone unit also increased 13.3% to $841.

The advent of 5G smartphones has lifted Apple's fortunes big time, driving an increase in both shipments and ASP. This is unlikely to change given the massive installed base of users in an upgrade window and Apple's impressive pricing.

The good news for Apple is that 5G smartphones are still in their early phases of growth. They accounted for just under 40% of total smartphone shipments in Q1. IDC estimates that 5G smartphones will account for nearly 70% of overall shipments of 1.53 billion units by 2025, which means that they will hit 1 billion in shipments by that year.

Apple has already gotten off to a solid start in this market, and it could keep winning big in the long run as well if it continues to hold on to its impressive share. That's why investors on the hunt for a 5G stock should take a closer look at Apple.

The stock is trading at 27 times trailing earnings, well below last year's average price-to-earnings (P/E) ratio of 40. The price-to-sales (P/S) ratio of 6.5 is also below the 2020 average of 8.47. This makes Apple an enticing pick for growth investors as it has switched into a higher gear and can be bought at a cheaper valuation than last year.

2. Chewy

Chewy stock has lost nearly a quarter of its value in 2021 despite posting outstanding growth recently that trounced Wall Street's expectations, hamstrung by fears of a drop-off in sales in a post-pandemic scenario. But its results and guidance provide clear indications that the rapid pace of growth is here to stay for the long run.

The company forecasts 30% to 31% revenue growth for the first quarter of fiscal 2021, which ended in April. Chewy is forecasting 24% to 25% top-line growth for the full year, along with an increase of 50 basis points to 100 basis points in the adjusted EBITDA (earnings before interest, taxes, depreciation, and amortization) margin. The annual outlook wouldn't have been so strong if online sales of pet products and supplies were to actually fall once people started coming out of their homes.

What makes Chewy's sharp pullback even more surprising is the fact that it occupies a dominant position in a nascent industry that's worth several billion dollars. Chewy management pointed out on the March earnings conference call that the share of online sales of pet products and supplies in the U.S. jumped to 30% last year from 7% in 2015. By 2025, that share is expected to jump to 53%.

The pet products and services market in the U.S. was worth an estimated $107 billion last year, which means that the online channel accounted for just over $32 billion in sales. Given that Chewy delivered $7.15 billion in sales in fiscal 2020, it can be assumed that its share of the online pet retail market stands at more than 22%.

Chewy could witness a sharp improvement in revenue in the coming years if it manages to hold on to even 20% of the online pet retail space in the U.S. The good part is that the company looks capable of sustaining its strong position in this market over the long run, given the pace at which it is adding new customers.

Chewy ended fiscal 2020 with 19.2 million active customers, an increase of 43% over the prior period. What's more, just over 68% of Chewy's sales during the year came from the Autoship subscription channel, indicating that the company is building a sustainable customer base that should help it take advantage of the end-market growth over time.

Finally, Chewy trades at less than 3.9 times sales right now, lower than the company's average P/S ratio of 5.6 last year. All of this makes it an enticing growth stock to buy right away, as analysts expect it to deliver triple-digit earnings growth in the long run.

An illustration shows Micron Technology computer chips

Image source: Micron Technology.

3. Micron Technology

Trading at less than eight times forward earnings, Micron Technology stock is terribly cheap right now for a company that's delivering huge top- and bottom-line growth. The company's price-to-sales ratio of 3.7 is also lower than last year's average of nearly four, and that's despite the fact that it was growing at a slower pace last year.

Micron's fiscal 2020 revenue (ending on Sept. 3, 2020) was down on a year-over-year basis. The memory specialist's fortunes have changed since, as its revenue for the first six months of the current fiscal year is up close to 21% year over year. But this is just the beginning.

The company anticipates 31% year-over-year revenue growth in Q3 to $7.1 billion, while earnings could nearly double. Analysts expect the momentum to continue for the remainder of the year and spill over into fiscal 2022. Consensus estimates project 25% revenue growth for fiscal 2021 and more than a 31% increase next year. Earnings per share are expected to nearly double in both fiscal years, driven by several catalysts. The chipmaker has several tailwinds driving demand for memory chips, such as data centers, personal computers (PCs), and smartphones.

The spurt in sales of 5G smartphones, for instance, has turned out to be a boon for Micron's mobile business unit (MBU), which recorded 44% year-over-year revenue growth last quarter and accounted for 29% of total revenue. We have already discussed that the 5G smartphone market has a lot of room to grow, which bodes well for Micron's MBU that's benefiting from a combination of higher volumes and more memory content in the new generation devices.

Additionally, the overall memory market's outlook suggests that Micron's rapid pace of growth is here to stay. Global Market Insights forecasts that the memory market could clock an annual growth rate of nearly 14% through 2026. Throw in a short supply of memory chips, and it becomes easier to understand why the favorable memory pricing environment Micron is thriving in is all set to continue.

Not surprisingly, analysts expect the company's bottom-line growth rate to double over the next five years compared to the previous five years. So, Micron is yet another solid example of a growth stock trading at an attractive valuation that you could buy right now.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.