66781928 has 8 divisors (see below), whose sum is σ = 125216130. Its totient is φ = 33390960.

The previous prime is 66781927. The next prime is 66781931. The reversal of 66781928 is 82918766.

It can be written as a sum of positive squares in only one way, i.e., 63329764 + 3452164 = 7958^2 + 1858^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is not an unprimeable number, because it can be changed into a prime (66781921) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4173863 + ... + 4173878.

Almost surely, 2^66781928 is an apocalyptic number.

It is an amenable number.

66781928 is a deficient number, since it is larger than the sum of its proper divisors (58434202).

66781928 is a wasteful number, since it uses less digits than its factorization.

66781928 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8347747 (or 8347743 counting only the distinct ones).

The product of its digits is 290304, while the sum is 47.

The square root of 66781928 is about 8172.0210474521. The cubic root of 66781928 is about 405.7136793994.

The spelling of 66781928 in words is "sixty-six million, seven hundred eighty-one thousand, nine hundred twenty-eight".