What numbers are divisible by 80?

A number is a multiple of 80 if the last 4 digits are a multiple of 80

• The 1,000s digit is even and the last 3 digits are a multiple of 80
• The 1,000s digit is odd and the last 3 digits are 40 times an odd number

It also works if the number is a multiple of 5 and 16 at the same time because 80 = 2^4 x 5 = 16 x 5