81640768751 has 16 divisors (see below), whose sum is σ = 84109054848. Its totient is φ = 79205817600.

The previous prime is 81640768733. The next prime is 81640768753. The reversal of 81640768751 is 15786704618.

It is a cyclic number.

It is not a de Polignac number, because 81640768751 - 2⁶ = 81640768687 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 81640768693 and 81640768702.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81640768753) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2647361 + ... + 2678021.

It is an arithmetic number, because the mean of its divisors is an integer number (5256815928).

Almost surely, 2^81640768751 is an apocalyptic number.

81640768751 is a deficient number, since it is larger than the sum of its proper divisors (2468286097).

81640768751 is a wasteful number, since it uses less digits than its factorization.

81640768751 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 31202.

The product of its (nonzero) digits is 2257920, while the sum is 53.

The spelling of 81640768751 in words is "eighty-one billion, six hundred forty million, seven hundred sixty-eight thousand, seven hundred fifty-one".