Adding together huge numbers with a large base/radix

[mrblister]

I want to add (and multiply) very large numbers in Excel, in Base36.

What I've been doing is using this formula to convert my (Base36) input values to decimals (Base10), and then convert the answer to Base36.
=BASE(DECIMAL("A00000000",36)*DECIMAL("100",36),36).
Note: Answer should be "A0000000000".
The formula was working fine, but the above formula gives an error. I think it's because converting the above values to decimal (and then multiplying them) creates a decimal number too large for Excel to handle.

Can anyone recommend a simple way to add/multiply/etc. large numbers in Excel in a different radix (Base36 in my case). The maximum size I'll be working with a 12 digit Base36 number, and I just want to add or subtract and perform other math operations (e.g. "Floor") on that number.

 

[BSALV]

that answer, that; i can give you without calculator !
Multiply with "100" in base36 is adding 2 zeros.
It becomes more difficult if you multiply with another number.

 

[BSALV]

Map1
	A	B	C	D	E	F
1	base36		base10
2	A00000000	----->	28.211.099.074.560	translate to base10	9
3	123	----->	1.371	translate to base11
4	product		3,86774E+16	multiply
5
6			2,82111E+12	<---your max = 36^8 = your biggest number
7
8	AKU	<------------	13710	divide A4 / A6
9	00000000	<------------	0	A4 MOD A6
10
11	AKU00000000			Join	11
12
Blad1

Cell Formulas
Range	Formula
E2,E11	E2	=LEN(A2)
C2:C3	C2	=DECIMAL(A2,36)
C4	C4	=+C3*C2
C6	C6	=POWER(36,8)
A8	A8	=BASE(C8,36)
A9	A9	=RIGHT(REPT("0",8)&BASE(C9,36),8)
C8	C8	=+C4/C6
C9	C9	=MOD(C4,C6)
A11	A11	=A8&A9