31072813 has 4 divisors (see below), whose sum is σ = 31244668. Its totient is φ = 30900960.

The previous prime is 31072799. The next prime is 31072817. The reversal of 31072813 is 31827013.

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 6441444 + 24631369 = 2538^2 + 4963^2 .

It is a cyclic number.

It is not a de Polignac number, because 31072813 - 2¹⁷ = 30941741 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 (31072817) 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, 85656 + ... + 86017.

It is an arithmetic number, because the mean of its divisors is an integer number (7811167).

Almost surely, 2^31072813 is an apocalyptic number.

It is an amenable number.

31072813 is a deficient number, since it is larger than the sum of its proper divisors (171855).

31072813 is a wasteful number, since it uses less digits than its factorization.

31072813 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 171854.

The product of its (nonzero) digits is 1008, while the sum is 25.

The square root of 31072813 is about 5574.2993281667. The cubic root of 31072813 is about 314.3838227653.

Adding to 31072813 its reverse (31827013), we get a palindrome (62899826).

The spelling of 31072813 in words is "thirty-one million, seventy-two thousand, eight hundred thirteen".