21042321 has 4 divisors (see below), whose sum is σ = 28056432. Its totient is φ = 14028212.

The previous prime is 21042319. The next prime is 21042347. The reversal of 21042321 is 12324012.

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 21042321 - 2¹ = 21042319 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21042321.

It is not an unprimeable number, because it can be changed into a prime (21542321) 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, 3507051 + ... + 3507056.

It is an arithmetic number, because the mean of its divisors is an integer number (7014108).

Almost surely, 2^21042321 is an apocalyptic number.

It is an amenable number.

21042321 is a deficient number, since it is larger than the sum of its proper divisors (7014111).

21042321 is an equidigital number, since it uses as much as digits as its factorization.

21042321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7014110.

The product of its (nonzero) digits is 96, while the sum is 15.

The square root of 21042321 is about 4587.1909705178. The cubic root of 21042321 is about 276.0776272930.

Adding to 21042321 its reverse (12324012), we get a palindrome (33366333).

The spelling of 21042321 in words is "twenty-one million, forty-two thousand, three hundred twenty-one".