The CAS Registry Mumber 3156-75-0 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 3,1,5 and 6 respectively; the second part has 2 digits, 7 and 5 respectively. Calculate Digit Verification of CAS Registry Number 3156-75: (6*3)+(5*1)+(4*5)+(3*6)+(2*7)+(1*5)=80 80 % 10 = 0 So 3156-75-0 is a valid CAS Registry Number.