The CAS Registry Mumber 84640-34-6 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,4,6,4 and 0 respectively; the second part has 2 digits, 3 and 4 respectively. Calculate Digit Verification of CAS Registry Number 84640-34: (7*8)+(6*4)+(5*6)+(4*4)+(3*0)+(2*3)+(1*4)=136 136 % 10 = 6 So 84640-34-6 is a valid CAS Registry Number.