31291681 has 4 divisors (see below), whose sum is σ = 31421764. Its totient is φ = 31161600.

The previous prime is 31291649. The next prime is 31291693. The reversal of 31291681 is 18619213.

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 22648081 + 8643600 = 4759^2 + 2940^2 .

It is a cyclic number.

It is not a de Polignac number, because 31291681 - 2⁵ = 31291649 is a prime.

It is a super-2 number, since 2×31291681² = 1958338599611522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (31211681) 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, 64680 + ... + 65161.

It is an arithmetic number, because the mean of its divisors is an integer number (7855441).

Almost surely, 2^31291681 is an apocalyptic number.

It is an amenable number.

31291681 is a deficient number, since it is larger than the sum of its proper divisors (130083).

31291681 is a wasteful number, since it uses less digits than its factorization.

31291681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 130082.

The product of its digits is 2592, while the sum is 31.

The square root of 31291681 is about 5593.8967634378. The cubic root of 31291681 is about 315.1202396434.

The spelling of 31291681 in words is "thirty-one million, two hundred ninety-one thousand, six hundred eighty-one".