There are two ordinary rules, common to all numbers.
Code: PD
P=8, (k=2)
Formulae:
Number N is divisible by 10 iff -2b+a is divisible by 10
Example:
P=8
Number N = 025750
-2( 2575)+0 =
-2(-2( 257+5)+0 =
-2(-2(-2( 25+7)+5)+0 =
-2(-2(-2(-2*2+5)+7)+5)+0 =
-2(-2(-2* 1+7)+5)+0 =
-2(-2* 5+5)+0
-2* 5+0 = 0 (mod 10)
is divisible by 10.
