The CAS Registry Mumber 82826-31-1 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,2,8,2 and 6 respectively; the second part has 2 digits, 3 and 1 respectively. Calculate Digit Verification of CAS Registry Number 82826-31: (7*8)+(6*2)+(5*8)+(4*2)+(3*6)+(2*3)+(1*1)=141 141 % 10 = 1 So 82826-31-1 is a valid CAS Registry Number.