31691357391 has 4 divisors (see below), whose sum is σ = 42255143192. Its totient is φ = 21127571592.

The previous prime is 31691357377. The next prime is 31691357419. The reversal of 31691357391 is 19375319613.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 31691357391 - 2¹¹ = 31691355343 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 31691357391.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (31691357351) 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, 5281892896 + ... + 5281892901.

It is an arithmetic number, because the mean of its divisors is an integer number (10563785798).

Almost surely, 2^31691357391 is an apocalyptic number.

31691357391 is a deficient number, since it is larger than the sum of its proper divisors (10563785801).

31691357391 is a wasteful number, since it uses less digits than its factorization.

31691357391 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10563785800.

The product of its digits is 459270, while the sum is 48.

The spelling of 31691357391 in words is "thirty-one billion, six hundred ninety-one million, three hundred fifty-seven thousand, three hundred ninety-one".