The 1921 Morgan silver dollar contains 0.77344 troy ounces of silver. Therefore, the silver value of a 1921 Morgan silver dollar is approximately 0.77344 * $24.30 = $18.80.
Please note that the silver value of a coin may vary based on market conditions and fluctuations in the price of silver. It's always a good idea to check current market prices to determine the exact silver value of a coin. Additionally, factors like condition, rarity, and collector demand can also affect the value of coins beyond their metal content.