81265766399 has 4 divisors (see below), whose sum is σ = 81450882480. Its totient is φ = 81080650320.

The previous prime is 81265766363. The next prime is 81265766401. The reversal of 81265766399 is 99366756218.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81265766399 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81265766359) 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, 92557382 + ... + 92558259.

It is an arithmetic number, because the mean of its divisors is an integer number (20362720620).

Almost surely, 2^81265766399 is an apocalyptic number.

81265766399 is a deficient number, since it is larger than the sum of its proper divisors (185116081).

81265766399 is a wasteful number, since it uses less digits than its factorization.

81265766399 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 185116080.

The product of its digits is 29393280, while the sum is 62.

The spelling of 81265766399 in words is "eighty-one billion, two hundred sixty-five million, seven hundred sixty-six thousand, three hundred ninety-nine".