The number of decks in a Blackjack game can affect both the odds and strategy. With more decks, the house edge increases slightly because it's harder to track the remaining cards, reducing the player's ability to gain an advantage, especially when using card counting. In single-deck games, card counting is more effective, and the odds of receiving a Blackjack are slightly better for the player. As the number of decks increases, the chances of getting a Blackjack decrease, and the dealer's chances of busting are lower due to a more balanced distribution of cards. Basic strategy also changes, with players needing to be more conservative in multi-deck games and adjusting their decisions for higher or lower risk. In essence, fewer decks generally offer an advantage to the player, while more decks slightly favor the house.