Alright, let's work through 83405209 times 79840871 step by step
83405209 × 79840871 = 79840871 × (83405209)
+ 79840871 × 9 yielding 718567839
+ 79840871 × 00 resulting in 0
+ 79840871 × 200 giving us 15968174200
+ 79840871 × 5000 producing 399204355000
+ 79840871 × 00000 that results in 0
+ 79840871 × 400000 that equals 31936348400000
+ 79840871 × 3000000 giving us 239522613000000
+ 79840871 × 80000000 giving us 6387269680000000

= 6659144532497039
