The CAS Registry Mumber 1185-31-5 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 1,1,8 and 5 respectively; the second part has 2 digits, 3 and 1 respectively. Calculate Digit Verification of CAS Registry Number 1185-31: (6*1)+(5*1)+(4*8)+(3*5)+(2*3)+(1*1)=65 65 % 10 = 5 So 1185-31-5 is a valid CAS Registry Number.