The CAS Registry Mumber 108657-69-8 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,0,8,6,5 and 7 respectively; the second part has 2 digits, 6 and 9 respectively. Calculate Digit Verification of CAS Registry Number 108657-69: (8*1)+(7*0)+(6*8)+(5*6)+(4*5)+(3*7)+(2*6)+(1*9)=148 148 % 10 = 8 So 108657-69-8 is a valid CAS Registry Number.