The CAS Registry Mumber 136764-84-6 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,3,6,7,6 and 4 respectively; the second part has 2 digits, 8 and 4 respectively. Calculate Digit Verification of CAS Registry Number 136764-84: (8*1)+(7*3)+(6*6)+(5*7)+(4*6)+(3*4)+(2*8)+(1*4)=156 156 % 10 = 6 So 136764-84-6 is a valid CAS Registry Number.