31981391 has 6 divisors (see below), whose sum is σ = 34630920. Its totient is φ = 29521128.

The previous prime is 31981361. The next prime is 31981399. The reversal of 31981391 is 19318913.

It is not a de Polignac number, because 31981391 - 2¹⁴ = 31965007 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 (31981399) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 94451 + ... + 94788.

It is an arithmetic number, because the mean of its divisors is an integer number (5771820).

Almost surely, 2^31981391 is an apocalyptic number.

31981391 is a deficient number, since it is larger than the sum of its proper divisors (2649529).

31981391 is a wasteful number, since it uses less digits than its factorization.

31981391 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 189265 (or 189252 counting only the distinct ones).

The product of its digits is 5832, while the sum is 35.

The square root of 31981391 is about 5655.2091915331. The cubic root of 31981391 is about 317.4186569058.

The spelling of 31981391 in words is "thirty-one million, nine hundred eighty-one thousand, three hundred ninety-one".