The CAS Registry Mumber 73672-81-8 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,3,6,7 and 2 respectively; the second part has 2 digits, 8 and 1 respectively. Calculate Digit Verification of CAS Registry Number 73672-81: (7*7)+(6*3)+(5*6)+(4*7)+(3*2)+(2*8)+(1*1)=148 148 % 10 = 8 So 73672-81-8 is a valid CAS Registry Number.