28444721 has 4 divisors (see below), whose sum is σ = 29681472. Its totient is φ = 27207972.

The previous prime is 28444709. The next prime is 28444739. The reversal of 28444721 is 12744482.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 28444721 - 2⁶ = 28444657 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (28444751) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 618341 + ... + 618386.

It is an arithmetic number, because the mean of its divisors is an integer number (7420368).

Almost surely, 2^28444721 is an apocalyptic number.

It is an amenable number.

28444721 is a deficient number, since it is larger than the sum of its proper divisors (1236751).

28444721 is a wasteful number, since it uses less digits than its factorization.

28444721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1236750.

The product of its digits is 14336, while the sum is 32.

The square root of 28444721 is about 5333.3592603536. The cubic root of 28444721 is about 305.2581206477.

The spelling of 28444721 in words is "twenty-eight million, four hundred forty-four thousand, seven hundred twenty-one".