21024409 has 4 divisors (see below), whose sum is σ = 24027904. Its totient is φ = 18020916.

The previous prime is 21024407. The next prime is 21024413. The reversal of 21024409 is 90442012.

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 21024409 - 2¹ = 21024407 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21024409.

It is not an unprimeable number, because it can be changed into a prime (21024403) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1501737 + ... + 1501750.

It is an arithmetic number, because the mean of its divisors is an integer number (6006976).

Almost surely, 2^21024409 is an apocalyptic number.

It is an amenable number.

21024409 is a deficient number, since it is larger than the sum of its proper divisors (3003495).

21024409 is an equidigital number, since it uses as much as digits as its factorization.

21024409 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3003494.

The product of its (nonzero) digits is 576, while the sum is 22.

The square root of 21024409 is about 4585.2381617534. The cubic root of 21024409 is about 275.9992692342. Note that the first 3 decimals are identical.

The spelling of 21024409 in words is "twenty-one million, twenty-four thousand, four hundred nine".