The CAS Registry Mumber 3359-72-6 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 3,3,5 and 9 respectively; the second part has 2 digits, 7 and 2 respectively. Calculate Digit Verification of CAS Registry Number 3359-72: (6*3)+(5*3)+(4*5)+(3*9)+(2*7)+(1*2)=96 96 % 10 = 6 So 3359-72-6 is a valid CAS Registry Number.