deux puissance quatre-cent-cinq
2^405=2^(5x81)
=(2^5)^(9x9)
=(32^3)^27
=(((326768)^3)^3)^3
=82631996098781074868989413504096379978550585370535152410581099409300723904538918228148651304964410605948901503127919788032
=8.2631996098781074868989413504096379978550585370535152410... × 10^121
l'ordre de grandeur est donc 10^122
