81607564091 has 2 divisors, whose sum is σ = 81607564092. Its totient is φ = 81607564090.

The previous prime is 81607564079. The next prime is 81607564109. The reversal of 81607564091 is 19046570618.

Together with next prime (81607564109) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81607564091 - 2¹⁸ = 81607301947 is a prime.

It is not a weakly prime, because it can be changed into another prime (81607564391) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40803782045 + 40803782046.

It is an arithmetic number, because the mean of its divisors is an integer number (40803782046).

Almost surely, 2^81607564091 is an apocalyptic number.

81607564091 is a deficient number, since it is larger than the sum of its proper divisors (1).

81607564091 is an equidigital number, since it uses as much as digits as its factorization.

81607564091 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 362880, while the sum is 47.

The spelling of 81607564091 in words is "eighty-one billion, six hundred seven million, five hundred sixty-four thousand, ninety-one".