21028369 has 4 divisors (see below), whose sum is σ = 21044800. Its totient is φ = 21011940.

The previous prime is 21028363. The next prime is 21028379. The reversal of 21028369 is 96382012.

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 21028369 - 2³ = 21028361 is a prime.

It is a super-2 number, since 2×21028369² = 884384605600322, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21028369.

It is not an unprimeable number, because it can be changed into a prime (21028361) 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, 6117 + ... + 8914.

It is an arithmetic number, because the mean of its divisors is an integer number (5261200).

Almost surely, 2^21028369 is an apocalyptic number.

It is an amenable number.

21028369 is a deficient number, since it is larger than the sum of its proper divisors (16431).

21028369 is a wasteful number, since it uses less digits than its factorization.

21028369 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16430.

The product of its (nonzero) digits is 5184, while the sum is 31.

The square root of 21028369 is about 4585.6699619576. The cubic root of 21028369 is about 276.0165965305.

The spelling of 21028369 in words is "twenty-one million, twenty-eight thousand, three hundred sixty-nine".