The CAS Registry Mumber 5360-21-4 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 5,3,6 and 0 respectively; the second part has 2 digits, 2 and 1 respectively. Calculate Digit Verification of CAS Registry Number 5360-21: (6*5)+(5*3)+(4*6)+(3*0)+(2*2)+(1*1)=74 74 % 10 = 4 So 5360-21-4 is a valid CAS Registry Number.