21. Hisoblang: 10⁴ + 2 · 10³ + 5 · 10² + 6 · 10 + 2

Darajalarni hisoblaymiz: 10⁴ = 10000, 10³ = 1000, 10² = 100.

Ko‘paytirishlarni bajaramiz: 2 · 1000 = 2000, 5 · 100 = 500, 6 · 10 = 60.

Yig‘amiz: 10000 + 2000 + 500 + 60 + 2 = 12562.

Javob: 12562.