The CAS Registry Mumber 190371-83-6 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,9,0,3,7 and 1 respectively; the second part has 2 digits, 8 and 3 respectively. Calculate Digit Verification of CAS Registry Number 190371-83: (8*1)+(7*9)+(6*0)+(5*3)+(4*7)+(3*1)+(2*8)+(1*3)=136 136 % 10 = 6 So 190371-83-6 is a valid CAS Registry Number.