The CAS Registry Mumber 75864-72-1 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,5,8,6 and 4 respectively; the second part has 2 digits, 7 and 2 respectively. Calculate Digit Verification of CAS Registry Number 75864-72: (7*7)+(6*5)+(5*8)+(4*6)+(3*4)+(2*7)+(1*2)=171 171 % 10 = 1 So 75864-72-1 is a valid CAS Registry Number.