81309963065 has 4 divisors (see below), whose sum is σ = 97571955684. Its totient is φ = 65047970448.

The previous prime is 81309963061. The next prime is 81309963067. The reversal of 81309963065 is 56036990318.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 22916207161 + 58393755904 = 151381^2 + 241648^2 .

It is a cyclic number.

It is not a de Polignac number, because 81309963065 - 2² = 81309963061 is a prime.

It is a super-2 number, since 2×81309963065² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81309963061) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8130996302 + ... + 8130996311.

It is an arithmetic number, because the mean of its divisors is an integer number (24392988921).

Almost surely, 2^81309963065 is an apocalyptic number.

It is an amenable number.

81309963065 is a deficient number, since it is larger than the sum of its proper divisors (16261992619).

81309963065 is a wasteful number, since it uses less digits than its factorization.

81309963065 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16261992618.

The product of its (nonzero) digits is 1049760, while the sum is 50.

The spelling of 81309963065 in words is "eighty-one billion, three hundred nine million, nine hundred sixty-three thousand, sixty-five".