Even if you try to operate on this symbolically, it's extremely large.
x = exp(sym(2.8e10))
x =
vpa(x, 10)
ans =
∞
numberOfDigits = vpa(log10(x))
numberOfDigits =
12160245493.291051174231609729665
If you were able to write out x it would have over twelve billion digits.
What's the purpose of this calculation? What does S1+S2+S3 represent? I'd consider trying to find another way to compute that quantity that doesn't require combining numbers that vary by so so many orders of magnitude.