21579923 has 4 divisors (see below), whose sum is σ = 21629520. Its totient is φ = 21530328.

The previous prime is 21579913. The next prime is 21579931. The reversal of 21579923 is 32997512.

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 21579923 - 2¹⁴ = 21563539 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21579913) 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, 24140 + ... + 25017.

It is an arithmetic number, because the mean of its divisors is an integer number (5407380).

Almost surely, 2^21579923 is an apocalyptic number.

21579923 is a deficient number, since it is larger than the sum of its proper divisors (49597).

21579923 is an equidigital number, since it uses as much as digits as its factorization.

21579923 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 49596.

The product of its digits is 34020, while the sum is 38.

The square root of 21579923 is about 4645.4195720085. The cubic root of 21579923 is about 278.4090169920.

The spelling of 21579923 in words is "twenty-one million, five hundred seventy-nine thousand, nine hundred twenty-three".