Sixties is the correct spelling.
60!
The question has provided the correct answer, you spell 60 as sixty.
64 or sixty-four
Sixty-three.
The Greek word for "Sixty" is "εξήντα".
it is spelled sixty-five
Sixty-nine.
Sixty-six.
sixty two
61 is spelled out, sixty-one.
soixante
sixty seven
The number 60000 is spelled as "sixty thousand."