The CAS Registry Mumber 73159-16-7 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,3,1,5 and 9 respectively; the second part has 2 digits, 1 and 6 respectively. Calculate Digit Verification of CAS Registry Number 73159-16: (7*7)+(6*3)+(5*1)+(4*5)+(3*9)+(2*1)+(1*6)=127 127 % 10 = 7 So 73159-16-7 is a valid CAS Registry Number.