The CAS Registry Mumber 397849-98-8 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 3,9,7,8,4 and 9 respectively; the second part has 2 digits, 9 and 8 respectively. Calculate Digit Verification of CAS Registry Number 397849-98: (8*3)+(7*9)+(6*7)+(5*8)+(4*4)+(3*9)+(2*9)+(1*8)=238 238 % 10 = 8 So 397849-98-8 is a valid CAS Registry Number.