31389 has 4 divisors (see below), whose sum is σ = 41856. Its totient is φ = 20924.

The previous prime is 31387. The next prime is 31391. The reversal of 31389 is 98313.

31389 = 55² + 56² + ... + 63².

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: 98313 = 3 ⋅32771.

It is an interprime number because it is at equal distance from previous prime (31387) and next prime (31391).

It is a cyclic number.

It is not a de Polignac number, because 31389 - 2¹ = 31387 is a prime.

It is a D-number.

31389 is a lucky number.

It is a nialpdrome in base 14.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (31387) 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, 5229 + ... + 5234.

It is an arithmetic number, because the mean of its divisors is an integer number (10464).

2³¹³⁸⁹ is an apocalyptic number.

It is an amenable number.

31389 is a deficient number, since it is larger than the sum of its proper divisors (10467).

31389 is a wasteful number, since it uses less digits than its factorization.

31389 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10466.

The product of its digits is 648, while the sum is 24.

The square root of 31389 is about 177.1694104523. The cubic root of 31389 is about 31.5446582494.

Adding to 31389 its sum of digits (24), we get a palindrome (31413).

The spelling of 31389 in words is "thirty-one thousand, three hundred eighty-nine".