81971457877 has 2 divisors, whose sum is σ = 81971457878. Its totient is φ = 81971457876.

The previous prime is 81971457863. The next prime is 81971457881. The reversal of 81971457877 is 77875417918.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 67040084241 + 14931373636 = 258921^2 + 122194^2 .

It is a cyclic number.

It is not a de Polignac number, because 81971457877 - 2⁷ = 81971457749 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81971457077) 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, 40985728938 + 40985728939.

It is an arithmetic number, because the mean of its divisors is an integer number (40985728939).

Almost surely, 2^81971457877 is an apocalyptic number.

It is an amenable number.

81971457877 is a deficient number, since it is larger than the sum of its proper divisors (1).

81971457877 is an equidigital number, since it uses as much as digits as its factorization.

81971457877 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 27659520, while the sum is 64.

The spelling of 81971457877 in words is "eighty-one billion, nine hundred seventy-one million, four hundred fifty-seven thousand, eight hundred seventy-seven".