31561681 has 8 divisors (see below), whose sum is σ = 32999040. Its totient is φ = 30129792.

The previous prime is 31561669. The next prime is 31561693. The reversal of 31561681 is 18616513.

It is an interprime number because it is at equal distance from previous prime (31561669) and next prime (31561693).

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-31561681 is a prime.

It is a super-2 number, since 2×31561681² = 1992279415091522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (31561631) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 14460 + ... + 16498.

It is an arithmetic number, because the mean of its divisors is an integer number (4124880).

Almost surely, 2^31561681 is an apocalyptic number.

It is an amenable number.

31561681 is a deficient number, since it is larger than the sum of its proper divisors (1437359).

31561681 is a wasteful number, since it uses less digits than its factorization.

31561681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2735.

The product of its digits is 4320, while the sum is 31.

The square root of 31561681 is about 5617.9783730449. The cubic root of 31561681 is about 316.0239827175.

The spelling of 31561681 in words is "thirty-one million, five hundred sixty-one thousand, six hundred eighty-one".