The CAS Registry Mumber 123358-25-8 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,2,3,3,5 and 8 respectively; the second part has 2 digits, 2 and 5 respectively. Calculate Digit Verification of CAS Registry Number 123358-25: (8*1)+(7*2)+(6*3)+(5*3)+(4*5)+(3*8)+(2*2)+(1*5)=108 108 % 10 = 8 So 123358-25-8 is a valid CAS Registry Number.