21805093 has 4 divisors (see below), whose sum is σ = 21931308. Its totient is φ = 21678880.

The previous prime is 21805079. The next prime is 21805117. The reversal of 21805093 is 39050812.

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 21224449 + 580644 = 4607^2 + 762^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21805093 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 (21805073) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 62848 + ... + 63193.

It is an arithmetic number, because the mean of its divisors is an integer number (5482827).

Almost surely, 2^21805093 is an apocalyptic number.

It is an amenable number.

21805093 is a deficient number, since it is larger than the sum of its proper divisors (126215).

21805093 is a wasteful number, since it uses less digits than its factorization.

21805093 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 126214.

The product of its (nonzero) digits is 2160, while the sum is 28.

The square root of 21805093 is about 4669.5923804975. The cubic root of 21805093 is about 279.3739968801.

The spelling of 21805093 in words is "twenty-one million, eight hundred five thousand, ninety-three".