The CAS Registry Mumber 85815-28-7 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,5,8,1 and 5 respectively; the second part has 2 digits, 2 and 8 respectively. Calculate Digit Verification of CAS Registry Number 85815-28: (7*8)+(6*5)+(5*8)+(4*1)+(3*5)+(2*2)+(1*8)=157 157 % 10 = 7 So 85815-28-7 is a valid CAS Registry Number.