The CAS Registry Mumber 78613-88-4 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,8,6,1 and 3 respectively; the second part has 2 digits, 8 and 8 respectively. Calculate Digit Verification of CAS Registry Number 78613-88: (7*7)+(6*8)+(5*6)+(4*1)+(3*3)+(2*8)+(1*8)=164 164 % 10 = 4 So 78613-88-4 is a valid CAS Registry Number.