31231913 has 4 divisors (see below), whose sum is σ = 31361748. Its totient is φ = 31102080.

The previous prime is 31231903. The next prime is 31231919. The reversal of 31231913 is 31913213.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 31913213 = 23 ⋅1387531.

It can be written as a sum of positive squares in 2 ways, for example, as 14845609 + 16386304 = 3853^2 + 4048^2 .

It is a cyclic number.

It is not a de Polignac number, because 31231913 - 2⁴ = 31231897 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (31231919) 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, 64556 + ... + 65037.

It is an arithmetic number, because the mean of its divisors is an integer number (7840437).

Almost surely, 2^31231913 is an apocalyptic number.

It is an amenable number.

31231913 is a deficient number, since it is larger than the sum of its proper divisors (129835).

31231913 is a wasteful number, since it uses less digits than its factorization.

31231913 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 129834.

The product of its digits is 486, while the sum is 23.

The square root of 31231913 is about 5588.5519591393. The cubic root of 31231913 is about 314.9194822339.

The spelling of 31231913 in words is "thirty-one million, two hundred thirty-one thousand, nine hundred thirteen".