The CAS Registry Mumber 361-13-7 includes 6 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 3 digits, 3,6 and 1 respectively; the second part has 2 digits, 1 and 3 respectively. Calculate Digit Verification of CAS Registry Number 361-13: (5*3)+(4*6)+(3*1)+(2*1)+(1*3)=47 47 % 10 = 7 So 361-13-7 is a valid CAS Registry Number.