31113991 has 4 divisors (see below), whose sum is σ = 31191984. Its totient is φ = 31036000.

The previous prime is 31113967. The next prime is 31114007. The reversal of 31113991 is 19931113.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 19931113 = 179 ⋅111347.

It is a cyclic number.

It is not a de Polignac number, because 31113991 - 2¹⁹ = 30589703 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 (31113911) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 38395 + ... + 39196.

It is an arithmetic number, because the mean of its divisors is an integer number (7797996).

Almost surely, 2^31113991 is an apocalyptic number.

31113991 is a deficient number, since it is larger than the sum of its proper divisors (77993).

31113991 is an equidigital number, since it uses as much as digits as its factorization.

31113991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 77992.

The product of its digits is 729, while the sum is 28.

The square root of 31113991 is about 5577.9916636725. The cubic root of 31113991 is about 314.5226363177.

The spelling of 31113991 in words is "thirty-one million, one hundred thirteen thousand, nine hundred ninety-one".