The CAS Registry Mumber 58377-56-3 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 5,8,3,7 and 7 respectively; the second part has 2 digits, 5 and 6 respectively. Calculate Digit Verification of CAS Registry Number 58377-56: (7*5)+(6*8)+(5*3)+(4*7)+(3*7)+(2*5)+(1*6)=163 163 % 10 = 3 So 58377-56-3 is a valid CAS Registry Number.