21028789 has 4 divisors (see below), whose sum is σ = 21233056. Its totient is φ = 20824524.

The previous prime is 21028771. The next prime is 21028823. The reversal of 21028789 is 98782012.

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 21028789 - 2⁷ = 21028661 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 (21028729) 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, 101979 + ... + 102184.

It is an arithmetic number, because the mean of its divisors is an integer number (5308264).

Almost surely, 2^21028789 is an apocalyptic number.

It is an amenable number.

21028789 is a deficient number, since it is larger than the sum of its proper divisors (204267).

21028789 is a wasteful number, since it uses less digits than its factorization.

21028789 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 204266.

The product of its (nonzero) digits is 16128, while the sum is 37.

The square root of 21028789 is about 4585.7157565641. The cubic root of 21028789 is about 276.0184341465.

The spelling of 21028789 in words is "twenty-one million, twenty-eight thousand, seven hundred eighty-nine".