320721 has 4 divisors (see below), whose sum is σ = 427632. Its totient is φ = 213812.

The previous prime is 320713. The next prime is 320741. The reversal of 320721 is 127023.

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 320721 - 2³ = 320713 is a prime.

It is a D-number.

It is a self number, because there is not a number n which added to its sum of digits gives 320721.

It is not an unprimeable number, because it can be changed into a prime (320741) 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, 53451 + ... + 53456.

It is an arithmetic number, because the mean of its divisors is an integer number (106908).

2³²⁰⁷²¹ is an apocalyptic number.

It is an amenable number.

320721 is a deficient number, since it is larger than the sum of its proper divisors (106911).

320721 is a wasteful number, since it uses less digits than its factorization.

320721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 106910.

The product of its (nonzero) digits is 84, while the sum is 15.

The square root of 320721 is about 566.3223463717. The cubic root of 320721 is about 68.4503698613.

Adding to 320721 its reverse (127023), we get a palindrome (447744).

The spelling of 320721 in words is "three hundred twenty thousand, seven hundred twenty-one", and thus it is an iban number.