21724089 has 4 divisors (see below), whose sum is σ = 28965456. Its totient is φ = 14482724.

The previous prime is 21724081. The next prime is 21724091. The reversal of 21724089 is 98042712.

It is a happy number.

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 21724089 - 2³ = 21724081 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21724081) 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, 3620679 + ... + 3620684.

It is an arithmetic number, because the mean of its divisors is an integer number (7241364).

Almost surely, 2^21724089 is an apocalyptic number.

It is an amenable number.

21724089 is a deficient number, since it is larger than the sum of its proper divisors (7241367).

21724089 is an equidigital number, since it uses as much as digits as its factorization.

21724089 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7241366.

The product of its (nonzero) digits is 8064, while the sum is 33.

The square root of 21724089 is about 4660.9107479118. The cubic root of 21724089 is about 279.0276176718.

The spelling of 21724089 in words is "twenty-one million, seven hundred twenty-four thousand, eighty-nine".