The CAS Registry Mumber 73116-15-1 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,3,1,1 and 6 respectively; the second part has 2 digits, 1 and 5 respectively. Calculate Digit Verification of CAS Registry Number 73116-15: (7*7)+(6*3)+(5*1)+(4*1)+(3*6)+(2*1)+(1*5)=101 101 % 10 = 1 So 73116-15-1 is a valid CAS Registry Number.