The CAS Registry Mumber 103826-80-8 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,0,3,8,2 and 6 respectively; the second part has 2 digits, 8 and 0 respectively. Calculate Digit Verification of CAS Registry Number 103826-80: (8*1)+(7*0)+(6*3)+(5*8)+(4*2)+(3*6)+(2*8)+(1*0)=108 108 % 10 = 8 So 103826-80-8 is a valid CAS Registry Number.