The CAS Registry Mumber 189939-44-4 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,8,9,9,3 and 9 respectively; the second part has 2 digits, 4 and 4 respectively. Calculate Digit Verification of CAS Registry Number 189939-44: (8*1)+(7*8)+(6*9)+(5*9)+(4*3)+(3*9)+(2*4)+(1*4)=214 214 % 10 = 4 So 189939-44-4 is a valid CAS Registry Number.