28721565 has 24 divisors (see below), whose sum is σ = 49908768. Its totient is φ = 15279840.

The previous prime is 28721557. The next prime is 28721573. The reversal of 28721565 is 56512782.

It is a happy number.

28721565 is a `hidden beast` number, since 28 + 72 + 1 + 565 = 666.

It is an interprime number because it is at equal distance from previous prime (28721557) and next prime (28721573).

It is not a de Polignac number, because 28721565 - 2³ = 28721557 is a prime.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 35010 + ... + 35820.

It is an arithmetic number, because the mean of its divisors is an integer number (2079532).

Almost surely, 2^28721565 is an apocalyptic number.

It is an amenable number.

28721565 is a deficient number, since it is larger than the sum of its proper divisors (21187203).

28721565 is a wasteful number, since it uses less digits than its factorization.

28721565 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1609 (or 1606 counting only the distinct ones).

The product of its digits is 33600, while the sum is 36.

The square root of 28721565 is about 5359.2504140038. The cubic root of 28721565 is about 306.2452538484.

The spelling of 28721565 in words is "twenty-eight million, seven hundred twenty-one thousand, five hundred sixty-five".