21075805 has 16 divisors (see below), whose sum is σ = 26319744. Its totient is φ = 16188480.

The previous prime is 21075781. The next prime is 21075809. The reversal of 21075805 is 50857012.

It is not a de Polignac number, because 21075805 - 2⁵ = 21075773 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 (21075809) by changing a digit.

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 15 ways as a sum of consecutive naturals, for example, 12312 + ... + 13918.

It is an arithmetic number, because the mean of its divisors is an integer number (1644984).

Almost surely, 2^21075805 is an apocalyptic number.

It is an amenable number.

21075805 is a deficient number, since it is larger than the sum of its proper divisors (5243939).

21075805 is a wasteful number, since it uses less digits than its factorization.

21075805 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1716.

The product of its (nonzero) digits is 2800, while the sum is 28.

The square root of 21075805 is about 4590.8392478936. The cubic root of 21075805 is about 276.2239876410.

The spelling of 21075805 in words is "twenty-one million, seventy-five thousand, eight hundred five".