81394248065 has 16 divisors (see below), whose sum is σ = 111373850448. Its totient is φ = 56570843136.

The previous prime is 81394248043. The next prime is 81394248137. The reversal of 81394248065 is 56084249318.

It can be written as a sum of positive squares in 8 ways, for example, as 443186704 + 80951061361 = 21052^2 + 284519^2 .

It is a cyclic number.

It is not a de Polignac number, because 81394248065 - 2¹² = 81394243969 is a prime.

It is a Duffinian number.

It is an unprimeable number.

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 in 15 ways as a sum of consecutive naturals, for example, 36828872 + ... + 36831081.

It is an arithmetic number, because the mean of its divisors is an integer number (6960865653).

Almost surely, 2^81394248065 is an apocalyptic number.

81394248065 is a gapful number since it is divisible by the number (85) formed by its first and last digit.

It is an amenable number.

81394248065 is a deficient number, since it is larger than the sum of its proper divisors (29979602383).

81394248065 is a wasteful number, since it uses less digits than its factorization.

81394248065 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 73659988.

The product of its (nonzero) digits is 1658880, while the sum is 50.

The spelling of 81394248065 in words is "eighty-one billion, three hundred ninety-four million, two hundred forty-eight thousand, sixty-five".