31609891 has 4 divisors (see below), whose sum is σ = 31900000. Its totient is φ = 31319784.

The previous prime is 31609883. The next prime is 31609931. The reversal of 31609891 is 19890613.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 19890613 = 127 ⋅156619.

It is a cyclic number.

It is not a de Polignac number, because 31609891 - 2³ = 31609883 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 31609891.

It is not an unprimeable number, because it can be changed into a prime (31609861) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 144891 + ... + 145108.

It is an arithmetic number, because the mean of its divisors is an integer number (7975000).

Almost surely, 2^31609891 is an apocalyptic number.

31609891 is a deficient number, since it is larger than the sum of its proper divisors (290109).

31609891 is a wasteful number, since it uses less digits than its factorization.

31609891 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 290108.

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

The square root of 31609891 is about 5622.2674251586. The cubic root of 31609891 is about 316.1848081759.

The spelling of 31609891 in words is "thirty-one million, six hundred nine thousand, eight hundred ninety-one".