21545439 has 16 divisors (see below), whose sum is σ = 29382144. Its totient is φ = 14040000.

The previous prime is 21545429. The next prime is 21545441. The reversal of 21545439 is 93454512.

It is not a de Polignac number, because 21545439 - 2⁷ = 21545311 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21545429) 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 15 ways as a sum of consecutive naturals, for example, 28314 + ... + 29064.

It is an arithmetic number, because the mean of its divisors is an integer number (1836384).

Almost surely, 2^21545439 is an apocalyptic number.

21545439 is a deficient number, since it is larger than the sum of its proper divisors (7836705).

21545439 is a wasteful number, since it uses less digits than its factorization.

21545439 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 958.

The product of its digits is 21600, while the sum is 33.

The square root of 21545439 is about 4641.7064749939. The cubic root of 21545439 is about 278.2606418112.

It can be divided in two parts, 215 and 45439, that added together give a palindrome (45654).

The spelling of 21545439 in words is "twenty-one million, five hundred forty-five thousand, four hundred thirty-nine".