The CAS Registry Mumber 28052-98-4 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 2,8,0,5 and 2 respectively; the second part has 2 digits, 9 and 8 respectively. Calculate Digit Verification of CAS Registry Number 28052-98: (7*2)+(6*8)+(5*0)+(4*5)+(3*2)+(2*9)+(1*8)=114 114 % 10 = 4 So 28052-98-4 is a valid CAS Registry Number.