What is 3000000000 500000000000000000000000000000000000000000000000000000000000000000000000000000?

The expression you've written appears to combine two large numbers: 3,000,000,000 and 500,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000. The first number is three billion, while the second is five hundred octillion (5 x 10^27). If you're looking for an operation such as addition, the sum would be 500,000,000,003,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000.