The CAS Registry Mumber 137435-09-7 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,3,7,4,3 and 5 respectively; the second part has 2 digits, 0 and 9 respectively. Calculate Digit Verification of CAS Registry Number 137435-09: (8*1)+(7*3)+(6*7)+(5*4)+(4*3)+(3*5)+(2*0)+(1*9)=127 127 % 10 = 7 So 137435-09-7 is a valid CAS Registry Number.