31231213 has 4 divisors (see below), whose sum is σ = 33633628. Its totient is φ = 28828800.

The previous prime is 31231139. The next prime is 31231223. The reversal of 31231213 is 31213213.

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 19245769 + 11985444 = 4387^2 + 3462^2 .

It is not a de Polignac number, because 31231213 - 2¹³ = 31223021 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 (31231223) 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, 1201188 + ... + 1201213.

It is an arithmetic number, because the mean of its divisors is an integer number (8408407).

Almost surely, 2^31231213 is an apocalyptic number.

It is an amenable number.

31231213 is a deficient number, since it is larger than the sum of its proper divisors (2402415).

31231213 is a wasteful number, since it uses less digits than its factorization.

31231213 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2402414.

The product of its digits is 108, while the sum is 16.

The square root of 31231213 is about 5588.4893307584. The cubic root of 31231213 is about 314.9171294558.

Adding to 31231213 its reverse (31213213), we get a palindrome (62444426).

The spelling of 31231213 in words is "thirty-one million, two hundred thirty-one thousand, two hundred thirteen".