The CAS Registry Mumber 4491-15-0 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 4,4,9 and 1 respectively; the second part has 2 digits, 1 and 5 respectively. Calculate Digit Verification of CAS Registry Number 4491-15: (6*4)+(5*4)+(4*9)+(3*1)+(2*1)+(1*5)=90 90 % 10 = 0 So 4491-15-0 is a valid CAS Registry Number.