21224309 has 4 divisors (see below), whose sum is σ = 21309120. Its totient is φ = 21139500.

The previous prime is 21224297. The next prime is 21224321. The reversal of 21224309 is 90342212.

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 an interprime number because it is at equal distance from previous prime (21224297) and next prime (21224321).

It is a cyclic number.

It is not a de Polignac number, because 21224309 - 2⁴ = 21224293 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 (21224389) 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, 42029 + ... + 42530.

It is an arithmetic number, because the mean of its divisors is an integer number (5327280).

Almost surely, 2^21224309 is an apocalyptic number.

It is an amenable number.

21224309 is a deficient number, since it is larger than the sum of its proper divisors (84811).

21224309 is an equidigital number, since it uses as much as digits as its factorization.

21224309 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 84810.

The product of its (nonzero) digits is 864, while the sum is 23.

The square root of 21224309 is about 4606.9848057054. The cubic root of 21224309 is about 276.8712447962.

The spelling of 21224309 in words is "twenty-one million, two hundred twenty-four thousand, three hundred nine".