78728666 has 32 divisors (see below), whose sum is σ = 134472960. Its totient is φ = 34338816.

The previous prime is 78728659. The next prime is 78728669. The reversal of 78728666 is 66682787.

It is a happy number.

It is a Smith number, since the sum of its digits (50) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is not an unprimeable number, because it can be changed into a prime (78728669) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 29066 + ... + 31658.

It is an arithmetic number, because the mean of its divisors is an integer number (4202280).

Almost surely, 2^78728666 is an apocalyptic number.

78728666 is a deficient number, since it is larger than the sum of its proper divisors (55744294).

78728666 is a wasteful number, since it uses less digits than its factorization.

78728666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2678.

The product of its digits is 1354752, while the sum is 50.

The square root of 78728666 is about 8872.9175585035. The cubic root of 78728666 is about 428.5922341116.

The spelling of 78728666 in words is "seventy-eight million, seven hundred twenty-eight thousand, six hundred sixty-six".