21024439 has 4 divisors (see below), whose sum is σ = 21039424. Its totient is φ = 21009456.

The previous prime is 21024433. The next prime is 21024457. The reversal of 21024439 is 93442012.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21024439 - 2⁵ = 21024407 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 (21024433) 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, 5142 + ... + 8275.

It is an arithmetic number, because the mean of its divisors is an integer number (5259856).

Almost surely, 2^21024439 is an apocalyptic number.

21024439 is a deficient number, since it is larger than the sum of its proper divisors (14985).

21024439 is a wasteful number, since it uses less digits than its factorization.

21024439 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14984.

The product of its (nonzero) digits is 1728, while the sum is 25.

The square root of 21024439 is about 4585.2414331200. The cubic root of 21024439 is about 275.9994005098. Note that the first 3 decimals are identical.

It can be divided in two parts, 210 and 24439, that added together give a square (24649 = 157²).

The spelling of 21024439 in words is "twenty-one million, twenty-four thousand, four hundred thirty-nine".