691321 has 4 divisors (see below), whose sum is σ = 694144. Its totient is φ = 688500.

The previous prime is 691309. The next prime is 691333. The reversal of 691321 is 123196.

691321 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 an interprime number because it is at equal distance from previous prime (691309) and next prime (691333).

It is a cyclic number.

It is not a de Polignac number, because 691321 - 2⁵ = 691289 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 691292 and 691301.

It is not an unprimeable number, because it can be changed into a prime (691381) 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, 1005 + ... + 1546.

It is an arithmetic number, because the mean of its divisors is an integer number (173536).

2⁶⁹¹³²¹ is an apocalyptic number.

It is an amenable number.

691321 is a deficient number, since it is larger than the sum of its proper divisors (2823).

691321 is a wasteful number, since it uses less digits than its factorization.

691321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2822.

The product of its digits is 324, while the sum is 22.

The square root of 691321 is about 831.4571546388. The cubic root of 691321 is about 88.4219150160.

The spelling of 691321 in words is "six hundred ninety-one thousand, three hundred twenty-one".