21944409 has 4 divisors (see below), whose sum is σ = 29259216. Its totient is φ = 14629604.

The previous prime is 21944393. The next prime is 21944413. The reversal of 21944409 is 90444912.

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 21944409 - 2⁴ = 21944393 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21944409.

It is not an unprimeable number, because it can be changed into a prime (21944009) 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 3 ways as a sum of consecutive naturals, for example, 3657399 + ... + 3657404.

It is an arithmetic number, because the mean of its divisors is an integer number (7314804).

Almost surely, 2^21944409 is an apocalyptic number.

It is an amenable number.

21944409 is a deficient number, since it is larger than the sum of its proper divisors (7314807).

21944409 is an equidigital number, since it uses as much as digits as its factorization.

21944409 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7314806.

The product of its (nonzero) digits is 10368, while the sum is 33.

The square root of 21944409 is about 4684.4859910133. The cubic root of 21944409 is about 279.9677216192.

The spelling of 21944409 in words is "twenty-one million, nine hundred forty-four thousand, four hundred nine".