The CAS Registry Mumber 18931-44-7 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 1,8,9,3 and 1 respectively; the second part has 2 digits, 4 and 4 respectively. Calculate Digit Verification of CAS Registry Number 18931-44: (7*1)+(6*8)+(5*9)+(4*3)+(3*1)+(2*4)+(1*4)=127 127 % 10 = 7 So 18931-44-7 is a valid CAS Registry Number.