81263715809 has 16 divisors (see below), whose sum is σ = 88217352720. Its totient is φ = 74554736640.

The previous prime is 81263715803. The next prime is 81263715829. The reversal of 81263715809 is 90851736218.

It can be written as a sum of positive squares in 8 ways, for example, as 10521015184 + 70742700625 = 102572^2 + 265975^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81263715809 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81263715803) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 782657 + ... + 880385.

It is an arithmetic number, because the mean of its divisors is an integer number (5513584545).

Almost surely, 2^81263715809 is an apocalyptic number.

It is an amenable number.

81263715809 is a deficient number, since it is larger than the sum of its proper divisors (6953636911).

81263715809 is a wasteful number, since it uses less digits than its factorization.

81263715809 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 98980.

The product of its (nonzero) digits is 725760, while the sum is 50.

The spelling of 81263715809 in words is "eighty-one billion, two hundred sixty-three million, seven hundred fifteen thousand, eight hundred nine".