321664 has 32 divisors (see below), whose sum is σ = 734400. Its totient is φ = 137472.

The previous prime is 321661. The next prime is 321679. The reversal of 321664 is 466123.

It is a tau number, because it is divible by the number of its divisors (32).

It is a nialpdrome in base 14.

It is not an unprimeable number, because it can be changed into a prime (321661) 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, 717 + ... + 1075.

It is an arithmetic number, because the mean of its divisors is an integer number (22950).

2³²¹⁶⁶⁴ is an apocalyptic number.

321664 is the 359-th heptagonal number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 321664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (367200).

321664 is an abundant number, since it is smaller than the sum of its proper divisors (412736).

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

321664 is an equidigital number, since it uses as much as digits as its factorization.

321664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 380 (or 368 counting only the distinct ones).

The product of its digits is 864, while the sum is 22.

The square root of 321664 is about 567.1542999925. The cubic root of 321664 is about 68.5173912899.

Adding to 321664 its reverse (466123), we get a palindrome (787787).

The spelling of 321664 in words is "three hundred twenty-one thousand, six hundred sixty-four".