31691 has 8 divisors (see below), whose sum is σ = 35904. Its totient is φ = 27720.

The previous prime is 31687. The next prime is 31699. The reversal of 31691 is 19613.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 31691 - 2² = 31687 is a prime.

It is a plaindrome in base 13.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 31691.

It is not an unprimeable number, because it can be changed into a prime (31699) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 440 + ... + 506.

It is an arithmetic number, because the mean of its divisors is an integer number (4488).

2³¹⁶⁹¹ is an apocalyptic number.

31691 is a deficient number, since it is larger than the sum of its proper divisors (4213).

31691 is a wasteful number, since it uses less digits than its factorization.

31691 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 121.

The product of its digits is 162, while the sum is 20.

The square root of 31691 is about 178.0196618354. The cubic root of 31691 is about 31.6455014000.

The spelling of 31691 in words is "thirty-one thousand, six hundred ninety-one".