21523889 has 4 divisors (see below), whose sum is σ = 22218240. Its totient is φ = 20829540.

The previous prime is 21523847. The next prime is 21523891. The reversal of 21523889 is 98832512.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21523889 - 2²⁴ = 4746673 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21523589) 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, 347129 + ... + 347190.

It is an arithmetic number, because the mean of its divisors is an integer number (5554560).

Almost surely, 2^21523889 is an apocalyptic number.

It is an amenable number.

21523889 is a deficient number, since it is larger than the sum of its proper divisors (694351).

21523889 is an equidigital number, since it uses as much as digits as its factorization.

21523889 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 694350.

The product of its digits is 34560, while the sum is 38.

The square root of 21523889 is about 4639.3845497005. The cubic root of 21523889 is about 278.1678376806.

The spelling of 21523889 in words is "twenty-one million, five hundred twenty-three thousand, eight hundred eighty-nine".