According to @TO, 21 is an important number in Bitcoin culture and explains why the Pizza Ninjas brand uses Pantone 21 as a background color. Source: @TO on X, Aug 10, 2025. This cultural focus aligns with Bitcoin’s fixed supply of 21,000,000 BTC, which is specified in the Bitcoin.org FAQ and underpins BTC’s scarcity narrative during trading cycles. Source: Bitcoin.org FAQ. For trading, monitoring spikes in search and social attention around '21' and related BTC narratives can serve as a sentiment proxy linked to price and volume dynamics. Source: Ladislav Kristoufek, Scientific Reports (2013), showing Google Trends and Wikipedia attention co-move with Bitcoin markets.