21534321 has 4 divisors (see below), whose sum is σ = 28712432. Its totient is φ = 14356212.

The previous prime is 21534301. The next prime is 21534323. The reversal of 21534321 is 12343512.

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 not a de Polignac number, because 21534321 - 2¹⁵ = 21501553 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21534323) 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, 3589051 + ... + 3589056.

It is an arithmetic number, because the mean of its divisors is an integer number (7178108).

Almost surely, 2^21534321 is an apocalyptic number.

It is an amenable number.

21534321 is a deficient number, since it is larger than the sum of its proper divisors (7178111).

21534321 is an equidigital number, since it uses as much as digits as its factorization.

21534321 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7178110.

The product of its digits is 720, while the sum is 21.

The square root of 21534321 is about 4640.5087005629. The cubic root of 21534321 is about 278.2127703628.

Adding to 21534321 its reverse (12343512), we get a palindrome (33877833).

The spelling of 21534321 in words is "twenty-one million, five hundred thirty-four thousand, three hundred twenty-one".