The CAS Registry Mumber 93131-78-3 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 9,3,1,3 and 1 respectively; the second part has 2 digits, 7 and 8 respectively. Calculate Digit Verification of CAS Registry Number 93131-78: (7*9)+(6*3)+(5*1)+(4*3)+(3*1)+(2*7)+(1*8)=123 123 % 10 = 3 So 93131-78-3 is a valid CAS Registry Number.