21244909 has 4 divisors (see below), whose sum is σ = 24279904. Its totient is φ = 18209916.

The previous prime is 21244903. The next prime is 21244913. The reversal of 21244909 is 90944212.

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 21244909 - 2¹⁷ = 21113837 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21244903) 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, 1517487 + ... + 1517500.

It is an arithmetic number, because the mean of its divisors is an integer number (6069976).

Almost surely, 2^21244909 is an apocalyptic number.

It is an amenable number.

21244909 is a deficient number, since it is larger than the sum of its proper divisors (3034995).

21244909 is an equidigital number, since it uses as much as digits as its factorization.

21244909 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3034994.

The product of its (nonzero) digits is 5184, while the sum is 31.

The square root of 21244909 is about 4609.2199990888. The cubic root of 21244909 is about 276.9607915415.

The spelling of 21244909 in words is "twenty-one million, two hundred forty-four thousand, nine hundred nine".