The CAS Registry Mumber 17216-94-3 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 1,7,2,1 and 6 respectively; the second part has 2 digits, 9 and 4 respectively. Calculate Digit Verification of CAS Registry Number 17216-94: (7*1)+(6*7)+(5*2)+(4*1)+(3*6)+(2*9)+(1*4)=103 103 % 10 = 3 So 17216-94-3 is a valid CAS Registry Number.