The number comes next in the series 12, 36, 109, 329, ... 990900800890

The given series doesn't seem to follow a simple arithmetic or geometric progression. However, if we look closely, we can see that each number is approximately three times the previous number.

Let's try to find a pattern:

1. 36 is approximately 3 times 12.
2. 109 is approximately 3 times 36.
3. 329 is approximately 3 times 109.

So, if we follow this pattern, the next number should be approximately 3 times 329.

Let's calculate:

329 * 3 = 987

However, the number you provided (990900800890) doesn't seem to fit this pattern. It's possible that there's a mistake in the series or the number you provided.