16320021 has 4 divisors (see below), whose sum is σ = 21760032. Its totient is φ = 10880012.

The previous prime is 16319999. The next prime is 16320023. The reversal of 16320021 is 12002361.

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 16320021 - 2¹⁵ = 16287253 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16320023) 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, 2720001 + ... + 2720006.

It is an arithmetic number, because the mean of its divisors is an integer number (5440008).

Almost surely, 2^16320021 is an apocalyptic number.

It is an amenable number.

16320021 is a deficient number, since it is larger than the sum of its proper divisors (5440011).

16320021 is an equidigital number, since it uses as much as digits as its factorization.

16320021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5440010.

The product of its (nonzero) digits is 72, while the sum is 15.

The square root of 16320021 is about 4039.8045744813. The cubic root of 16320021 is about 253.6531370126.

Adding to 16320021 its reverse (12002361), we get a palindrome (28322382).

The spelling of 16320021 in words is "sixteen million, three hundred twenty thousand, twenty-one".