The CAS Registry Mumber 3186-53-6 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 3,1,8 and 6 respectively; the second part has 2 digits, 5 and 3 respectively. Calculate Digit Verification of CAS Registry Number 3186-53: (6*3)+(5*1)+(4*8)+(3*6)+(2*5)+(1*3)=86 86 % 10 = 6 So 3186-53-6 is a valid CAS Registry Number.