321720 has 64 divisors (see below), whose sum is σ = 1105920. Its totient is φ = 73344.

The previous prime is 321709. The next prime is 321721. The reversal of 321720 is 27123.

321720 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

It is a Harshad number since it is a multiple of its sum of digits (15).

It is a self number, because there is not a number n which added to its sum of digits gives 321720.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 321720.

It is not an unprimeable number, because it can be changed into a prime (321721) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 649 + ... + 1031.

It is an arithmetic number, because the mean of its divisors is an integer number (17280).

2³²¹⁷²⁰ is an apocalyptic number.

321720 is a gapful number since it is divisible by the number (30) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 321720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (552960).

321720 is an abundant number, since it is smaller than the sum of its proper divisors (784200).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

321720 is a wasteful number, since it uses less digits than its factorization.

321720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 404 (or 400 counting only the distinct ones).

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

The square root of 321720 is about 567.2036671250. The cubic root of 321720 is about 68.5213672309.

Adding to 321720 its reverse (27123), we get a palindrome (348843).

The spelling of 321720 in words is "three hundred twenty-one thousand, seven hundred twenty", and thus it is an iban number.