21857923 has 4 divisors (see below), whose sum is σ = 23008360. Its totient is φ = 20707488.

The previous prime is 21857897. The next prime is 21857933. The reversal of 21857923 is 32975812.

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

It is a cyclic number.

It is not a de Polignac number, because 21857923 - 2⁹ = 21857411 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21857933) 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, 575190 + ... + 575227.

It is an arithmetic number, because the mean of its divisors is an integer number (5752090).

Almost surely, 2^21857923 is an apocalyptic number.

21857923 is a deficient number, since it is larger than the sum of its proper divisors (1150437).

21857923 is a wasteful number, since it uses less digits than its factorization.

21857923 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1150436.

The product of its digits is 30240, while the sum is 37.

The square root of 21857923 is about 4675.2457689409. The cubic root of 21857923 is about 279.5994399987.

The spelling of 21857923 in words is "twenty-one million, eight hundred fifty-seven thousand, nine hundred twenty-three".