81679690681 has 2 divisors, whose sum is σ = 81679690682. Its totient is φ = 81679690680.

The previous prime is 81679690669. The next prime is 81679690721. The reversal of 81679690681 is 18609697618.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 78185107456 + 3494583225 = 279616^2 + 59115^2 .

It is a cyclic number.

It is not a de Polignac number, because 81679690681 - 2⁵ = 81679690649 is a prime.

It is a super-2 number, since 2×81679690681² (a number of 23 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (81679690601) 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, 40839845340 + 40839845341.

It is an arithmetic number, because the mean of its divisors is an integer number (40839845341).

Almost surely, 2^81679690681 is an apocalyptic number.

It is an amenable number.

81679690681 is a deficient number, since it is larger than the sum of its proper divisors (1).

81679690681 is an equidigital number, since it uses as much as digits as its factorization.

81679690681 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 7838208, while the sum is 61.

The spelling of 81679690681 in words is "eighty-one billion, six hundred seventy-nine million, six hundred ninety thousand, six hundred eighty-one".