The CAS Registry Mumber 102831-76-5 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,0,2,8,3 and 1 respectively; the second part has 2 digits, 7 and 6 respectively. Calculate Digit Verification of CAS Registry Number 102831-76: (8*1)+(7*0)+(6*2)+(5*8)+(4*3)+(3*1)+(2*7)+(1*6)=95 95 % 10 = 5 So 102831-76-5 is a valid CAS Registry Number.