28766721 has 16 divisors (see below), whose sum is σ = 40513536. Its totient is φ = 18119376.

The previous prime is 28766713. The next prime is 28766783. The reversal of 28766721 is 12766782.

It is not a de Polignac number, because 28766721 - 2³ = 28766713 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 28766721.

It is not an unprimeable number, because it can be changed into a prime (28766711) 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, 3216 + ... + 8238.

It is an arithmetic number, because the mean of its divisors is an integer number (2532096).

Almost surely, 2^28766721 is an apocalyptic number.

It is an amenable number.

28766721 is a deficient number, since it is larger than the sum of its proper divisors (11746815).

28766721 is a wasteful number, since it uses less digits than its factorization.

28766721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5132.

The product of its digits is 56448, while the sum is 39.

The square root of 28766721 is about 5363.4616620239. The cubic root of 28766721 is about 306.4056625842.

The spelling of 28766721 in words is "twenty-eight million, seven hundred sixty-six thousand, seven hundred twenty-one".