28656421 has 4 divisors (see below), whose sum is σ = 28678752. Its totient is φ = 28634092.

The previous prime is 28656409. The next prime is 28656451. The reversal of 28656421 is 12465682.

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, and also an emirpimes, since its reverse is a distinct semiprime: 12465682 = 2 ⋅6232841.

It is a cyclic number.

It is not a de Polignac number, because 28656421 - 2⁷ = 28656293 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28656401) 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, 9115 + ... + 11848.

It is an arithmetic number, because the mean of its divisors is an integer number (7169688).

Almost surely, 2^28656421 is an apocalyptic number.

It is an amenable number.

28656421 is a deficient number, since it is larger than the sum of its proper divisors (22331).

28656421 is a wasteful number, since it uses less digits than its factorization.

28656421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22330.

The product of its digits is 23040, while the sum is 34.

The square root of 28656421 is about 5353.1692482118. The cubic root of 28656421 is about 306.0135447605.

The spelling of 28656421 in words is "twenty-eight million, six hundred fifty-six thousand, four hundred twenty-one".