31281565681 has 2 divisors, whose sum is σ = 31281565682. Its totient is φ = 31281565680.

The previous prime is 31281565661. The next prime is 31281565703. The reversal of 31281565681 is 18656518213.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 30272868081 + 1008697600 = 173991^2 + 31760^2 .

It is an emirp because it is prime and its reverse (18656518213) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 31281565681 - 2²⁷ = 31147347953 is a prime.

It is a super-2 number, since 2×31281565681² (a number of 22 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (31281565631) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15640782840 + 15640782841.

It is an arithmetic number, because the mean of its divisors is an integer number (15640782841).

Almost surely, 2^31281565681 is an apocalyptic number.

It is an amenable number.

31281565681 is a deficient number, since it is larger than the sum of its proper divisors (1).

31281565681 is an equidigital number, since it uses as much as digits as its factorization.

31281565681 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 345600, while the sum is 46.

The spelling of 31281565681 in words is "thirty-one billion, two hundred eighty-one million, five hundred sixty-five thousand, six hundred eighty-one".