It's a question frequently typed into Google, as evidenced by the search predictions: Is Indy 500 Formula 1? No, it's not. But the links between the two are growing all the time.
The parallels are nothing new, of course. There have been multiple champions of both categories - Mario Andretti, Emerson Fittipaldi, Nigel Mansell and Jacques Villeneuve.
This year's Indy 500 winner Marcus Ericsson spent fours years in F1 between 2014 and 2018, but never came anywhere near close to scaling the lofty heights he managed this past Sunday at The Brickyard.
Exclusively racing in machinery that never had any hope of matching the might of Mercedes through the turbo hybrid era of Formula 1, Ericsson's stock barely rose in the 97 race starts he made.
From those, just 11 resulted in a points finish and, even in his brightest season in 2018, he was overshadowed by the fast-emerging talent of a certain Charles Leclerc.
A step back in time…
It used to be the case, certainly back in the 1990s, that an IndyCar title winner could be lured across the pond to F1 fairly readily. That happened with Villeneuve, Michael Andretti, Juan Pablo Montoya and Alex Zanardi, with varying levels of success.
But now, with Mansell's 1993 campaign and Fernando Alonso's Indy 500 appearances having had something of a novelty value, the connections are much more deep seated.
And a big part of that has to be the greater number of opportunities available to drivers in IndyCar than Formula 1.
F1 is regarded as the pinnacle of motorsport, the true elite class with only 20 prized seats available. But of course, those places are not acquired on talent alone - a driver also has to bring significant financial backing with him, sometimes even from his own family.
As Ericsson drenched himself with the traditional winner's bottle of milk after his third race victory Stateside for the Chip Ganassi team, he knew he had beaten a field of 33 - only 13 of which were drivers from the United States.
F1 connections run deep
Indeed, along with the Swede, there were nine other Europeans - all of whom have either raced or tested in Formula 1 or, surely, have dreamt of doing so at some stage.
Romain Grosjean needs no introduction, of course. He crashed out at Indy, as did Callum Ilott, a member of the Ferrari Academy who appeared in two FP1 sessions for Alfa Romeo last year.
Unable to prise open the door to an F1 race seat, Ilott, runner-up to Mick Schumacher in the 2020 F2 championship, is trying his luck in IndyCar, likewise Christian Lundgaard, another of the European 10 at the Brickyard.
The two youngsters have yet to make a big breakthrough and Grosjean is still seeking a first win but Ericsson, whose best F1 result in five full seasons was eighth in the 2015 Australian Grand Prix for Sauber, has shown what can be achieved. With double points available for the Indy 500, he now leads this year's championship.
However, let's not suggest the solidified Indy-F1 links are merely limited to young hopefuls packing their bags hoping to find fame and fortune in the States, or veterans prolonging their career for one last shot at glory. It goes significantly further than that.
McLaren's presence is looming large
And a big reason for that is McLaren. They, of course, were behind Alonso's Indy 500 tilts when the Spaniard even took the 2017 Monaco Grand Prix off to boost his chances of completing the Triple Crown, while the Spaniard had two more goes while on his F1 sabbatical in 2020 and 2021.
Arrow McLaren SP Racing fielded the runner-up to Ericsson in the Indy 500, Pato O'Ward, who has already tested for the Woking-based constructor in F1 and is set to take part in a free practice session for them this season as part of fulfilling the rookie driver requirement.
Having recently signed a three-year contract extension, the Mexican could therefore find himself in contention as a potential team-mate for Lando Norris one day - although one of his IndyCar rivals may just have designs on that position too.
That is Colton Herta, who does not compete for Arrow McLaren SP, instead being part of the rival Andretti operation, and yet has been signed on for a development programme by Zak Brown, the McLaren Racing CEO.
Brown spoke earlier this year about McLaren trying to bring F1 and IndyCar closer together.
"We are McLaren Racing and Formula 1 is clearly our centre of gravity, if you like," said the 50-year-old Californian.
"But I think as a single racing entity, if we can tie our racing programs together, I think it looks fantastic to be able to look at both [F1 and Indy] cars and go 'yep, that's a McLaren' regardless of what racing series you are looking at."
Is F1 a threat to IndyCar in the US?
Should IndyCar feel threatened by the rapid rise of F1 in the US, with the popularity of Netflix docuseries 'Drive to Survive' and a third grand prix scheduled for 2023 in Las Vegas?
Clearly not, as shown not only by Ericsson enjoying the greatest moment of his racing career at the age of 31, but also the plans of Andretti to establish an F1 team from 2024 that are currently awaiting approval from the FIA.
Along with Ganassi and Penske, Andretti is one of the premier team names in the IndyCar Series and that is extremely unlikely to change in the foreseeable future, whatever transpires with the F1 project.
Therefore, as McLaren would obviously concur, the world's two most prestigious single-seater categories can co-exist perfectly happily.
And the cementing of that relationship can only be a good thing for motorsport in general.