231691 has 4 divisors (see below), whose sum is σ = 237384. Its totient is φ = 226000.

The previous prime is 231677. The next prime is 231701. The reversal of 231691 is 196132.

231691 = 194² + 195² + ... + 199².

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 231691 - 2⁷ = 231563 is a prime.

It is a Smith number, since the sum of its digits (22) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (231611) 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, 2785 + ... + 2866.

It is an arithmetic number, because the mean of its divisors is an integer number (59346).

2²³¹⁶⁹¹ is an apocalyptic number.

231691 is a deficient number, since it is larger than the sum of its proper divisors (5693).

231691 is an equidigital number, since it uses as much as digits as its factorization.

231691 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5692.

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

The square root of 231691 is about 481.3429131087. The cubic root of 231691 is about 61.4190443388.

The spelling of 231691 in words is "two hundred thirty-one thousand, six hundred ninety-one".