31399391 has 4 divisors (see below), whose sum is σ = 33246432. Its totient is φ = 29552352.

The previous prime is 31399369. The next prime is 31399411. The reversal of 31399391 is 19399313.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-31399391 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 (31393391) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 923495 + ... + 923528.

It is an arithmetic number, because the mean of its divisors is an integer number (8311608).

Almost surely, 2^31399391 is an apocalyptic number.

31399391 is a deficient number, since it is larger than the sum of its proper divisors (1847041).

31399391 is a wasteful number, since it uses less digits than its factorization.

31399391 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1847040.

The product of its digits is 19683, while the sum is 38.

The square root of 31399391 is about 5603.5159498301. The cubic root of 31399391 is about 315.4813870841.

The spelling of 31399391 in words is "thirty-one million, three hundred ninety-nine thousand, three hundred ninety-one".