The CAS Registry Mumber 3620-08-4 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 3,6,2 and 0 respectively; the second part has 2 digits, 0 and 8 respectively. Calculate Digit Verification of CAS Registry Number 3620-08: (6*3)+(5*6)+(4*2)+(3*0)+(2*0)+(1*8)=64 64 % 10 = 4 So 3620-08-4 is a valid CAS Registry Number.