The CAS Registry Mumber 72676-16-5 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, 1 and 6 respectively. Calculate Digit Verification of CAS Registry Number 72676-16: (7*7)+(6*2)+(5*6)+(4*7)+(3*6)+(2*1)+(1*6)=145 145 % 10 = 5 So 72676-16-5 is a valid CAS Registry Number.