The CAS Registry Mumber 83851-72-3 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,3,8,5 and 1 respectively; the second part has 2 digits, 7 and 2 respectively. Calculate Digit Verification of CAS Registry Number 83851-72: (7*8)+(6*3)+(5*8)+(4*5)+(3*1)+(2*7)+(1*2)=153 153 % 10 = 3 So 83851-72-3 is a valid CAS Registry Number.