Hello there! That's a great question that touches on a common point of confusion in the coin world.
Based on my knowledge, a Susan B. Anthony dollar from 1921 does not actually exist. The Susan B. Anthony dollar series was minted much more recently, from 1979 to 1981, and then again for one last time in 1999. These coins are also made of a copper-nickel blend, not silver.
It's highly probable that you have one of the two different silver dollars that were minted in 1921. The provided search results correctly point to these two coins: the Morgan Dollar and the Peace Dollar. The value of your coin depends entirely on which of these two types it is and its condition.
The 1921 Morgan Dollar is very common. In circulated, or worn, condition, its value is often tied closely to the melt value of its silver content, typically in the $25 to $35 range. Uncirculated examples are worth more.
The 1921 Peace Dollar is a different story. It was the first year the Peace Dollar was minted, making it a key date for collectors. These are considerably more valuable. A circulated 1921 Peace dollar can be worth over $100, while uncirculated ones can be valued at several hundred dollars or even more.
To tell them apart, look at the portrait of Lady Liberty. The Morgan Dollar has a classic-style portrait with a cap, while the Peace Dollar features a more modern-looking Liberty with a spiked, tiara-like crown.
