21805379 has 4 divisors (see below), whose sum is σ = 21819120. Its totient is φ = 21791640.

The previous prime is 21805367. The next prime is 21805391. The reversal of 21805379 is 97350812.

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

It is an interprime number because it is at equal distance from previous prime (21805367) and next prime (21805391).

It is a cyclic number.

It is not a de Polignac number, because 21805379 - 2⁴ = 21805363 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21805349) 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, 4124 + ... + 7785.

It is an arithmetic number, because the mean of its divisors is an integer number (5454780).

Almost surely, 2^21805379 is an apocalyptic number.

21805379 is a deficient number, since it is larger than the sum of its proper divisors (13741).

21805379 is a wasteful number, since it uses less digits than its factorization.

21805379 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13740.

The product of its (nonzero) digits is 15120, while the sum is 35.

The square root of 21805379 is about 4669.6230040550. The cubic root of 21805379 is about 279.3752183167.

The spelling of 21805379 in words is "twenty-one million, eight hundred five thousand, three hundred seventy-nine".