The CAS Registry Mumber 74397-36-7 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,4,3,9 and 7 respectively; the second part has 2 digits, 3 and 6 respectively. Calculate Digit Verification of CAS Registry Number 74397-36: (7*7)+(6*4)+(5*3)+(4*9)+(3*7)+(2*3)+(1*6)=157 157 % 10 = 7 So 74397-36-7 is a valid CAS Registry Number.