321681 has 4 divisors (see below), whose sum is σ = 428912. Its totient is φ = 214452.

The previous prime is 321679. The next prime is 321707. The reversal of 321681 is 186123.

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 not a de Polignac number, because 321681 - 2¹ = 321679 is a prime.

It is a super-2 number, since 2×321681² = 206957331522, which contains 22 as substring.

It is a D-number.

It is a Duffinian number.

It is a nialpdrome in base 14.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 321681.

It is not an unprimeable number, because it can be changed into a prime (321611) 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, 53611 + ... + 53616.

It is an arithmetic number, because the mean of its divisors is an integer number (107228).

2³²¹⁶⁸¹ is an apocalyptic number.

It is an amenable number.

321681 is a deficient number, since it is larger than the sum of its proper divisors (107231).

321681 is a wasteful number, since it uses less digits than its factorization.

321681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 107230.

The product of its digits is 288, while the sum is 21.

The square root of 321681 is about 567.1692868977. The cubic root of 321681 is about 68.5185983208.

The spelling of 321681 in words is "three hundred twenty-one thousand, six hundred eighty-one".