28918021 has 4 divisors (see below), whose sum is σ = 31546944. Its totient is φ = 26289100.

The previous prime is 28917953. The next prime is 28918031. The reversal of 28918021 is 12081982.

It is a happy number.

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 28918021 - 2⁷ = 28917893 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28918031) 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, 1314445 + ... + 1314466.

It is an arithmetic number, because the mean of its divisors is an integer number (7886736).

Almost surely, 2^28918021 is an apocalyptic number.

It is an amenable number.

28918021 is a deficient number, since it is larger than the sum of its proper divisors (2628923).

28918021 is a wasteful number, since it uses less digits than its factorization.

28918021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2628922.

The product of its (nonzero) digits is 2304, while the sum is 31.

The square root of 28918021 is about 5377.5478612468. The cubic root of 28918021 is about 306.9419088167.

The spelling of 28918021 in words is "twenty-eight million, nine hundred eighteen thousand, twenty-one".