31813 has 4 divisors (see below), whose sum is σ = 32940. Its totient is φ = 30688.

The previous prime is 31799. The next prime is 31817.

31813 is nontrivially palindromic in base 10.

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

It can be written as a sum of positive squares in 2 ways, for example, as 12769 + 19044 = 113^2 + 138^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-31813 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 (31817) 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, 520 + ... + 577.

It is an arithmetic number, because the mean of its divisors is an integer number (8235).

2³¹⁸¹³ is an apocalyptic number.

It is an amenable number.

31813 is a deficient number, since it is larger than the sum of its proper divisors (1127).

31813 is a wasteful number, since it uses less digits than its factorization.

31813 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1126.

The product of its digits is 72, while the sum is 16.

The square root of 31813 is about 178.3619914668. The cubic root of 31813 is about 31.6860576834.

The spelling of 31813 in words is "thirty-one thousand, eight hundred thirteen".