Might be Echinocactus grusonii w/white spines. Do the spines have any ridges or are they smooth? Smooth = grusonii.
I know for a fact it's not Echonocactus grusonii because I have 3 of them.
Sure looks like a baby 'Golden Barrel' to me.
You know it for a fact. Very definitive answer.
Small cacti bought from places where they are unnamed are often impossible to ID. There are several reasons for this. One being the fact that even the definition of a species is a man made construct. Lots of our named species show a wide variety of characteristics. For instance, some species of Mammillarias are said to be 'intermediate between species A and species B'. The reason for this is because the species in question might exhibit all the characteristics across its range. In the western part of the range, the flowers might be pink and the spines short, with one central and a dozen radials. On the eastern part of the range, the flowers might be predominantly white with no central spine and only 6 radial spines. Humans will come along and give each variant a different species name, but the plants are still able to cross-pollinate each other and produce viable seed.
A seed house gets this seed, grows the plant, sells it to a big box store where you buy it. The plant is still tiny, but you want an ID, so you go onto a website where the whole world can opine about the name of this unknown, could-be-a-hybrid plant. The provenance of the seed is in doubt, the plants was sold without a name, the store sells it as "Succulent", but you can state facts about the name? In the world of cactusdom, that is preposterous.
That said, I agree with plantomaniac, it looks like a tiny E. grusonii. Of course, Cactusboss, you have the advantage of being able to hold the plant, to examine it in detail. To better help with an ID for cactus plants, the spine details are important. The number of spines a plant has can vary within the species. The color can vary. But the shape of the spine (round or flat), the presence of the hook, the presence of transverse ridges, etc. all give clues for the probable ID or the plant. To help us, you need to answer questions.
For instance, does this one have transverse ridges? There are some small Ferocactus that look like your plant, especially from pictures on the internet. But almost all Feros have the ridges, even when as small as your plant. On the other hand, a smooth spine would indicate Echinocactus grusonii, no matter what facts you think you have.
I don't normally rant like this about an ID, but this morning I feel playful while I wait for the grass to dry. If you got your feelings hurt, it was not meant that way at all. I'm guessing you are a young person who has a plant addiction. I was there too. When RoRo was still in diapers, I was starting tomato seeds with my mother in a zone 3 climate. Optimism is a hallmark of plant addicts, I hope yours lasts as long as mine has. I still think your plant is a grusonii.
Here are my three E. grusonii's. It looks nothing like them.
Wait, you can't see any similarity besides the obvious round spikey thing? Well, all have felted aeroles. All have sharp flat spines. All have the tendency to have about 3 centrals. All have ribs.
Now small plants often have pointillated ribs (is that a term?) I'm meaning that instead of a continuous rib, they are like little peaks where the spines grow. A good extreme example is Ferocactus emoryi. I have grown them from seed, and until they get about 5 years old, the only thing they share with the parent is a hooked central and the color. (Not counting the transverse ridges that all Feros have.)
I hope the plant thrives and grows for you. In a few years, it could be that the true name will reveal itself, but until then, I still think it is a grusonii. Reasons? The general look of the plant, its very young age, the fact it probably came form a big box store (is this correct?) and they are commonly sold there.
Cultural conditions can effect the look of a plant, as well the variation within a species. If 3 seeds grow an Echinocereus and the plants are then grown in Kamloops, BC, San Diego, Cal. and Richmond,VA, it is entirely possible that the plants would develop differently. Strong sun makes strong colored spines, less sun makes for slower growth, and lots of rain and humidity can make the plant grow bark, commonly called corking.