1、3^21=10 460 353 203。
2、演算过程：
3^21=3*3^20
=3*(3^2)^10
=3*9^10
=3*(10-1)^10
=3*[10^10-c(10,1)*10^9+c(10,2)*10^8-c(10,3)*10^7+……+c(10,8)*10^2-c(10,9)*10+1]
=3*[45*10^8-120*10^7+210*10^6-252*10^5+210*10^4-120*10^3+45*10^2-10*10+1]
=3*[(33+2.1-0.252)*10^8+(21-1.2)*10^5+4500-100+1]
=3*[34.848*10^8+19.8*10^5+4500-100+1]
=3*[34848*10^5+19.8*10^5+4500-100+1]
=3*[34867.8*10^5+4401]
=104603.4*10^5+13203
=10460353203