It is not possible to answer the question since a single number, such as 1266918, does not make a sequence. Also, there is no simple partitioning of the given number into a set of numbers which make up a straightforward sequence.
108
3467910 is a single number: it is not a pattern!
Look at the difference between each number and the next number.
The next number is -21
it is 31818 - 8 = 1010 - 4 = 66 - 2 = 44 - 1 = 3
59 is the next number in this series.
The next number in the series is 67.
A single number such as 61205041320 does not make a series.
A single number, such as 12848384 does not make a series.
One number does not make a sequence (nor a series).
There is no series of number: just one very large number!
8
243
20
73791170
25
108