31987 has 4 divisors (see below), whose sum is σ = 33120. Its totient is φ = 30856.

The previous prime is 31981. The next prime is 31991. The reversal of 31987 is 78913.

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

It is not a de Polignac number, because 31987 - 2⁷ = 31859 is a prime.

It is a Duffinian number.

It is a zygodrome in base 2.

It is not an unprimeable number, because it can be changed into a prime (31981) 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, 523 + ... + 580.

It is an arithmetic number, because the mean of its divisors is an integer number (8280).

2³¹⁹⁸⁷ is an apocalyptic number.

31987 is a deficient number, since it is larger than the sum of its proper divisors (1133).

31987 is a wasteful number, since it uses less digits than its factorization.

31987 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1132.

The product of its digits is 1512, while the sum is 28.

The square root of 31987 is about 178.8490984042. The cubic root of 31987 is about 31.7437212459.

It can be divided in two parts, 319 and 87, that added together give a triangular number (406 = T₂₈).

The spelling of 31987 in words is "thirty-one thousand, nine hundred eighty-seven".