How much is 5E38?

E is how the calculator expresses overflow by using exponential notation. In most calculators 5E38 would mean 5×10^38.

E stands for exponent. 5 is the base and 38 is power.

15! and 26! are pretty damn big numbers. You calculator can’t display a number that big.

15! = 1,307,674,368,000
26! = 403,291,461,126,605,635,584,000,000

That’s (4×10^27)*(1.3×1013).

Good descriptions above.
Here are a couple of examples that might make it easy
5E2 is 500
4E4 is 40000
1E0 is 10
3.2E3 is 3200
Get the idea?

500,000,000,000,000,000,000,000,000,000,000,000,000

@CWOTUS You left off the (+20).