21028205 has 8 divisors (see below), whose sum is σ = 27527904. Its totient is φ = 15293200.

The previous prime is 21028181. The next prime is 21028211. The reversal of 21028205 is 50282012.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21028205 - 2⁸ = 21027949 is a prime.

It is a Duffinian number.

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 7 ways as a sum of consecutive naturals, for example, 191111 + ... + 191220.

It is an arithmetic number, because the mean of its divisors is an integer number (3440988).

Almost surely, 2^21028205 is an apocalyptic number.

It is an amenable number.

21028205 is a deficient number, since it is larger than the sum of its proper divisors (6499699).

21028205 is a wasteful number, since it uses less digits than its factorization.

21028205 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 382347.

The product of its (nonzero) digits is 320, while the sum is 20.

The square root of 21028205 is about 4585.6520801299. The cubic root of 21028205 is about 276.0158789786.

The spelling of 21028205 in words is "twenty-one million, twenty-eight thousand, two hundred five".