The CAS Registry Mumber 102998-52-7 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,0,2,9,9 and 8 respectively; the second part has 2 digits, 5 and 2 respectively. Calculate Digit Verification of CAS Registry Number 102998-52: (8*1)+(7*0)+(6*2)+(5*9)+(4*9)+(3*8)+(2*5)+(1*2)=137 137 % 10 = 7 So 102998-52-7 is a valid CAS Registry Number.