81766797857 has 2 divisors, whose sum is σ = 81766797858. Its totient is φ = 81766797856.

The previous prime is 81766797823. The next prime is 81766797883. The reversal of 81766797857 is 75879766718.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 61524337681 + 20242460176 = 248041^2 + 142276^2 .

It is a cyclic number.

It is not a de Polignac number, because 81766797857 - 2⁶ = 81766797793 is a prime.

It is not a weakly prime, because it can be changed into another prime (81766797157) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40883398928 + 40883398929.

It is an arithmetic number, because the mean of its divisors is an integer number (40883398929).

Almost surely, 2^81766797857 is an apocalyptic number.

It is an amenable number.

81766797857 is a deficient number, since it is larger than the sum of its proper divisors (1).

81766797857 is an equidigital number, since it uses as much as digits as its factorization.

81766797857 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 248935680, while the sum is 71.

The spelling of 81766797857 in words is "eighty-one billion, seven hundred sixty-six million, seven hundred ninety-seven thousand, eight hundred fifty-seven".