The CAS Registry Mumber 34633-31-3 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 3,4,6,3 and 3 respectively; the second part has 2 digits, 3 and 1 respectively. Calculate Digit Verification of CAS Registry Number 34633-31: (7*3)+(6*4)+(5*6)+(4*3)+(3*3)+(2*3)+(1*1)=103 103 % 10 = 3 So 34633-31-3 is a valid CAS Registry Number.