21904423 has 8 divisors (see below), whose sum is σ = 22635936. Its totient is φ = 21184800.

The previous prime is 21904411. The next prime is 21904427. The reversal of 21904423 is 32440912.

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

It is a cyclic number.

It is not a de Polignac number, because 21904423 - 2⁵ = 21904391 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21904427) 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 7 ways as a sum of consecutive naturals, for example, 853 + ... + 6673.

It is an arithmetic number, because the mean of its divisors is an integer number (2829492).

Almost surely, 2^21904423 is an apocalyptic number.

21904423 is a deficient number, since it is larger than the sum of its proper divisors (731513).

21904423 is an equidigital number, since it uses as much as digits as its factorization.

21904423 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5945.

The product of its (nonzero) digits is 1728, while the sum is 25.

The square root of 21904423 is about 4680.2161274881. The cubic root of 21904423 is about 279.7975705231.

The spelling of 21904423 in words is "twenty-one million, nine hundred four thousand, four hundred twenty-three".