31881 has 4 divisors (see below), whose sum is σ = 42512. Its totient is φ = 21252.

The previous prime is 31873. The next prime is 31883. The reversal of 31881 is 18813.

It is a happy number.

31881 is digitally balanced in base 4, 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, and also an emirpimes, since its reverse is a distinct semiprime: 18813 = 3 ⋅6271.

It is not a de Polignac number, because 31881 - 2³ = 31873 is a prime.

It is a super-2 number, since 2×31881² = 2032796322, which contains 22 as substring.

It is an Ulam number.

It is a D-number.

It is a Duffinian number.

It is a nialpdrome in base 8.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 31881.

It is not an unprimeable number, because it can be changed into a prime (31883) 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, 5311 + ... + 5316.

It is an arithmetic number, because the mean of its divisors is an integer number (10628).

2³¹⁸⁸¹ is an apocalyptic number.

It is an amenable number.

31881 is a deficient number, since it is larger than the sum of its proper divisors (10631).

31881 is a wasteful number, since it uses less digits than its factorization.

31881 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10630.

The product of its digits is 192, while the sum is 21.

The square root of 31881 is about 178.5525132839. The cubic root of 31881 is about 31.7086178376.

The spelling of 31881 in words is "thirty-one thousand, eight hundred eighty-one".