The CAS Registry Mumber 4747-16-4 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 4,7,4 and 7 respectively; the second part has 2 digits, 1 and 6 respectively. Calculate Digit Verification of CAS Registry Number 4747-16: (6*4)+(5*7)+(4*4)+(3*7)+(2*1)+(1*6)=104 104 % 10 = 4 So 4747-16-4 is a valid CAS Registry Number.