81387956669 has 4 divisors (see below), whose sum is σ = 81520727196. Its totient is φ = 81255186144.

The previous prime is 81387956659. The next prime is 81387956677. The reversal of 81387956669 is 96665978318.

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 10438708900 + 70949247769 = 102170^2 + 266363^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81387956669 is a prime.

It is a super-2 number, since 2×81387956669² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 81387956599 and 81387956608.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81387956659) 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, 66384344 + ... + 66385569.

It is an arithmetic number, because the mean of its divisors is an integer number (20380181799).

Almost surely, 2^81387956669 is an apocalyptic number.

It is an amenable number.

81387956669 is a deficient number, since it is larger than the sum of its proper divisors (132770527).

81387956669 is a wasteful number, since it uses less digits than its factorization.

81387956669 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 132770526.

The product of its digits is 117573120, while the sum is 68.

The spelling of 81387956669 in words is "eighty-one billion, three hundred eighty-seven million, nine hundred fifty-six thousand, six hundred sixty-nine".