The CAS Registry Mumber 588-33-0 includes 6 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 3 digits, 5,8 and 8 respectively; the second part has 2 digits, 3 and 3 respectively. Calculate Digit Verification of CAS Registry Number 588-33: (5*5)+(4*8)+(3*8)+(2*3)+(1*3)=90 90 % 10 = 0 So 588-33-0 is a valid CAS Registry Number.