The CAS Registry Mumber 72687-29-7 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,2,6,8 and 7 respectively; the second part has 2 digits, 2 and 9 respectively. Calculate Digit Verification of CAS Registry Number 72687-29: (7*7)+(6*2)+(5*6)+(4*8)+(3*7)+(2*2)+(1*9)=157 157 % 10 = 7 So 72687-29-7 is a valid CAS Registry Number.