>>540
2012京 > 2^x
lg 2012*10^16 > lg 2^x  (lg は底2の対数)
lg 2012*10^16 > x
log 2012*10^16 / log 2 > x   (log は底10の対数)
(16 + log 2012 )/ log2 > x

(16 + log(2012)) / log(2) ≒ 64.1252641

求めるxは65、
つまり 2012京 < 2^65

確認で
2^64      = 1.84 × 10^19
2012*10^16 = 2.01 × 10^19
2^65      = 3.68 × 10^19