The CAS Registry Mumber 715-27-5 includes 6 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 3 digits, 7,1 and 5 respectively; the second part has 2 digits, 2 and 7 respectively. Calculate Digit Verification of CAS Registry Number 715-27: (5*7)+(4*1)+(3*5)+(2*2)+(1*7)=65 65 % 10 = 5 So 715-27-5 is a valid CAS Registry Number.