31906891 has 2 divisors, whose sum is σ = 31906892. Its totient is φ = 31906890.

The previous prime is 31906883. The next prime is 31906939. The reversal of 31906891 is 19860913.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 31906891 - 2³ = 31906883 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 31906891.

It is not a weakly prime, because it can be changed into another prime (31906811) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15953445 + 15953446.

It is an arithmetic number, because the mean of its divisors is an integer number (15953446).

Almost surely, 2^31906891 is an apocalyptic number.

31906891 is the 3573-rd centered pentagonal number.

31906891 is a deficient number, since it is larger than the sum of its proper divisors (1).

31906891 is an equidigital number, since it uses as much as digits as its factorization.

31906891 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 11664, while the sum is 37.

The square root of 31906891 is about 5648.6185036697. The cubic root of 31906891 is about 317.1719918372.

The spelling of 31906891 in words is "thirty-one million, nine hundred six thousand, eight hundred ninety-one".