81687766879 has 2 divisors, whose sum is σ = 81687766880. Its totient is φ = 81687766878.

The previous prime is 81687766877. The next prime is 81687766933. The reversal of 81687766879 is 97866778618.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81687766879 - 2¹ = 81687766877 is a prime.

Together with 81687766877, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81687766873) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40843883439 + 40843883440.

It is an arithmetic number, because the mean of its divisors is an integer number (40843883440).

Almost surely, 2^81687766879 is an apocalyptic number.

81687766879 is a deficient number, since it is larger than the sum of its proper divisors (1).

81687766879 is an equidigital number, since it uses as much as digits as its factorization.

81687766879 is an evil number, because the sum of its binary digits is even.

The product of its digits is 341397504, while the sum is 73.

The spelling of 81687766879 in words is "eighty-one billion, six hundred eighty-seven million, seven hundred sixty-six thousand, eight hundred seventy-nine".