31861 has 4 divisors (see below), whose sum is σ = 32224. Its totient is φ = 31500.

The previous prime is 31859. The next prime is 31873. The reversal of 31861 is 16813.

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 a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 31861 - 2¹ = 31859 is a prime.

It is a Duffinian number.

It is a plaindrome in base 13.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (31891) 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, 46 + ... + 256.

It is an arithmetic number, because the mean of its divisors is an integer number (8056).

2³¹⁸⁶¹ is an apocalyptic number.

It is an amenable number.

31861 is a deficient number, since it is larger than the sum of its proper divisors (363).

31861 is a wasteful number, since it uses less digits than its factorization.

31861 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 362.

The product of its digits is 144, while the sum is 19.

The square root of 31861 is about 178.4964985651. The cubic root of 31861 is about 31.7019858309.

The spelling of 31861 in words is "thirty-one thousand, eight hundred sixty-one".