31931681 has 4 divisors (see below), whose sum is σ = 31951764. Its totient is φ = 31911600.

The previous prime is 31931663. The next prime is 31931693. The reversal of 31931681 is 18613913.

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

It can be written as a sum of positive squares in 2 ways, for example, as 1018081 + 30913600 = 1009^2 + 5560^2 .

It is a cyclic number.

It is not a de Polignac number, because 31931681 - 2⁶ = 31931617 is a prime.

It is a super-2 number, since 2×31931681² = 2039264502971522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (31931651) 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, 7430 + ... + 10911.

It is an arithmetic number, because the mean of its divisors is an integer number (7987941).

Almost surely, 2^31931681 is an apocalyptic number.

It is an amenable number.

31931681 is a deficient number, since it is larger than the sum of its proper divisors (20083).

31931681 is a wasteful number, since it uses less digits than its factorization.

31931681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20082.

The product of its digits is 3888, while the sum is 32.

The square root of 31931681 is about 5650.8124194668. The cubic root of 31931681 is about 317.2541126374.

The spelling of 31931681 in words is "thirty-one million, nine hundred thirty-one thousand, six hundred eighty-one".