The CAS Registry Mumber 83159-19-7 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,3,1,5 and 9 respectively; the second part has 2 digits, 1 and 9 respectively. Calculate Digit Verification of CAS Registry Number 83159-19: (7*8)+(6*3)+(5*1)+(4*5)+(3*9)+(2*1)+(1*9)=137 137 % 10 = 7 So 83159-19-7 is a valid CAS Registry Number.