The CAS Registry Mumber 4402-87-3 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 4,4,0 and 2 respectively; the second part has 2 digits, 8 and 7 respectively. Calculate Digit Verification of CAS Registry Number 4402-87: (6*4)+(5*4)+(4*0)+(3*2)+(2*8)+(1*7)=73 73 % 10 = 3 So 4402-87-3 is a valid CAS Registry Number.