21440321 has 8 divisors (see below), whose sum is σ = 24562560. Its totient is φ = 18332928.

The previous prime is 21440317. The next prime is 21440351. The reversal of 21440321 is 12304412.

21440321 is nontrivially palindromic in base 16.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21440321 - 2² = 21440317 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 21440321.

It is not an unprimeable number, because it can be changed into a prime (21440351) 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 7 ways as a sum of consecutive naturals, for example, 416 + ... + 6561.

It is an arithmetic number, because the mean of its divisors is an integer number (3070320).

Almost surely, 2^21440321 is an apocalyptic number.

It is an amenable number.

21440321 is a deficient number, since it is larger than the sum of its proper divisors (3122239).

21440321 is an equidigital number, since it uses as much as digits as its factorization.

21440321 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7423.

The product of its (nonzero) digits is 192, while the sum is 17.

The square root of 21440321 is about 4630.3694237069. The cubic root of 21440321 is about 277.8073687528.

Adding to 21440321 its reverse (12304412), we get a palindrome (33744733).

The spelling of 21440321 in words is "twenty-one million, four hundred forty thousand, three hundred twenty-one".