The CAS Registry Mumber 243137-98-6 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 2,4,3,1,3 and 7 respectively; the second part has 2 digits, 9 and 8 respectively. Calculate Digit Verification of CAS Registry Number 243137-98: (8*2)+(7*4)+(6*3)+(5*1)+(4*3)+(3*7)+(2*9)+(1*8)=126 126 % 10 = 6 So 243137-98-6 is a valid CAS Registry Number.