100000000000000000000 + 100000000000000000000 = 200000000000000000000
2*1020 this is called 200quintillion a quintillion is a number with 18 zeros a sextillion is a number with 21 zeros your number has 20 zeros therefore it is not quite a sextillion yet.
Two hundred quintillion.
200,000,000,000,000,000,000 200 billion billion or 200 million trillion