The CAS Registry Mumber 72676-81-4 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,2,6,7 and 6 respectively; the second part has 2 digits, 8 and 1 respectively. Calculate Digit Verification of CAS Registry Number 72676-81: (7*7)+(6*2)+(5*6)+(4*7)+(3*6)+(2*8)+(1*1)=154 154 % 10 = 4 So 72676-81-4 is a valid CAS Registry Number.