The CAS Registry Mumber 87033-44-1 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,7,0,3 and 3 respectively; the second part has 2 digits, 4 and 4 respectively. Calculate Digit Verification of CAS Registry Number 87033-44: (7*8)+(6*7)+(5*0)+(4*3)+(3*3)+(2*4)+(1*4)=131 131 % 10 = 1 So 87033-44-1 is a valid CAS Registry Number.