21075205 has 4 divisors (see below), whose sum is σ = 25290252. Its totient is φ = 16860160.

The previous prime is 21075181. The next prime is 21075217. The reversal of 21075205 is 50257012.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 5377761 + 15697444 = 2319^2 + 3962^2 .

It is not a de Polignac number, because 21075205 - 2⁷ = 21075077 is a prime.

It is a Smith number, since the sum of its digits (22) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2107516 + ... + 2107525.

It is an arithmetic number, because the mean of its divisors is an integer number (6322563).

Almost surely, 2^21075205 is an apocalyptic number.

It is an amenable number.

21075205 is a deficient number, since it is larger than the sum of its proper divisors (4215047).

21075205 is an equidigital number, since it uses as much as digits as its factorization.

21075205 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4215046.

The product of its (nonzero) digits is 700, while the sum is 22.

The square root of 21075205 is about 4590.7738998997. The cubic root of 21075205 is about 276.2213663735.

The spelling of 21075205 in words is "twenty-one million, seventy-five thousand, two hundred five".