The CAS Registry Mumber 136800-74-3 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,3,6,8,0 and 0 respectively; the second part has 2 digits, 7 and 4 respectively. Calculate Digit Verification of CAS Registry Number 136800-74: (8*1)+(7*3)+(6*6)+(5*8)+(4*0)+(3*0)+(2*7)+(1*4)=123 123 % 10 = 3 So 136800-74-3 is a valid CAS Registry Number.