The CAS Registry Mumber 51636-39-6 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 5,1,6,3 and 6 respectively; the second part has 2 digits, 3 and 9 respectively. Calculate Digit Verification of CAS Registry Number 51636-39: (7*5)+(6*1)+(5*6)+(4*3)+(3*6)+(2*3)+(1*9)=116 116 % 10 = 6 So 51636-39-6 is a valid CAS Registry Number.