The CAS Registry Mumber 136-61-8 includes 6 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 3 digits, 1,3 and 6 respectively; the second part has 2 digits, 6 and 1 respectively. Calculate Digit Verification of CAS Registry Number 136-61: (5*1)+(4*3)+(3*6)+(2*6)+(1*1)=48 48 % 10 = 8 So 136-61-8 is a valid CAS Registry Number.