The CAS Registry Mumber 64158-69-6 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 6,4,1,5 and 8 respectively; the second part has 2 digits, 6 and 9 respectively. Calculate Digit Verification of CAS Registry Number 64158-69: (7*6)+(6*4)+(5*1)+(4*5)+(3*8)+(2*6)+(1*9)=136 136 % 10 = 6 So 64158-69-6 is a valid CAS Registry Number.