21448409 has 4 divisors (see below), whose sum is σ = 21464016. Its totient is φ = 21432804.

The previous prime is 21448379. The next prime is 21448433. The reversal of 21448409 is 90484412.

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 21448409 - 2⁸ = 21448153 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21448909) 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, 5519 + ... + 8564.

It is an arithmetic number, because the mean of its divisors is an integer number (5366004).

Almost surely, 2^21448409 is an apocalyptic number.

It is an amenable number.

21448409 is a deficient number, since it is larger than the sum of its proper divisors (15607).

21448409 is a wasteful number, since it uses less digits than its factorization.

21448409 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15606.

The product of its (nonzero) digits is 9216, while the sum is 32.

The square root of 21448409 is about 4631.2427057972. The cubic root of 21448409 is about 277.8422970782.

The spelling of 21448409 in words is "twenty-one million, four hundred forty-eight thousand, four hundred nine".