31808656981 has 2 divisors, whose sum is σ = 31808656982. Its totient is φ = 31808656980.

The previous prime is 31808656949. The next prime is 31808657051. The reversal of 31808656981 is 18965680813.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 23571460900 + 8237196081 = 153530^2 + 90759^2 .

It is a cyclic number.

It is not a de Polignac number, because 31808656981 - 2⁵ = 31808656949 is a prime.

It is a super-2 number, since 2×31808656981² (a number of 22 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31008656981) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15904328490 + 15904328491.

It is an arithmetic number, because the mean of its divisors is an integer number (15904328491).

Almost surely, 2^31808656981 is an apocalyptic number.

It is an amenable number.

31808656981 is a deficient number, since it is larger than the sum of its proper divisors (1).

31808656981 is an equidigital number, since it uses as much as digits as its factorization.

31808656981 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2488320, while the sum is 55.

The spelling of 31808656981 in words is "thirty-one billion, eight hundred eight million, six hundred fifty-six thousand, nine hundred eighty-one".