81697583641 has 2 divisors, whose sum is σ = 81697583642. Its totient is φ = 81697583640.

The previous prime is 81697583567. The next prime is 81697583647. The reversal of 81697583641 is 14638579618.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 48708490000 + 32989093641 = 220700^2 + 181629^2 .

It is a cyclic number.

It is not a de Polignac number, because 81697583641 - 2²³ = 81689195033 is a prime.

It is not a weakly prime, because it can be changed into another prime (81697583647) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40848791820 + 40848791821.

It is an arithmetic number, because the mean of its divisors is an integer number (40848791821).

Almost surely, 2^81697583641 is an apocalyptic number.

It is an amenable number.

81697583641 is a deficient number, since it is larger than the sum of its proper divisors (1).

81697583641 is an equidigital number, since it uses as much as digits as its factorization.

81697583641 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 8709120, while the sum is 58.

The spelling of 81697583641 in words is "eighty-one billion, six hundred ninety-seven million, five hundred eighty-three thousand, six hundred forty-one".