31591 has 4 divisors (see below), whose sum is σ = 36112. Its totient is φ = 27072.

The previous prime is 31583. The next prime is 31601. The reversal of 31591 is 19513.

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 31591 - 2³ = 31583 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (31511) 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 3 ways as a sum of consecutive naturals, for example, 2250 + ... + 2263.

It is an arithmetic number, because the mean of its divisors is an integer number (9028).

2³¹⁵⁹¹ is an apocalyptic number.

31591 is a deficient number, since it is larger than the sum of its proper divisors (4521).

31591 is an equidigital number, since it uses as much as digits as its factorization.

31591 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4520.

The product of its digits is 135, while the sum is 19.

The square root of 31591 is about 177.7385720658. The cubic root of 31591 is about 31.6121808512.

It can be divided in two parts, 3159 and 1, that added together give a triangular number (3160 = T₇₉).

The spelling of 31591 in words is "thirty-one thousand, five hundred ninety-one".