81771878473 has 4 divisors (see below), whose sum is σ = 81774268308. Its totient is φ = 81769488640.

The previous prime is 81771878437. The next prime is 81771878491. The reversal of 81771878473 is 37487817718.

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 62813893129 + 18957985344 = 250627^2 + 137688^2 .

It is a cyclic number.

It is not a de Polignac number, because 81771878473 - 2²¹ = 81769781321 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81771278473) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 1142836 + ... + 1212277.

It is an arithmetic number, because the mean of its divisors is an integer number (20443567077).

Almost surely, 2^81771878473 is an apocalyptic number.

It is an amenable number.

81771878473 is a deficient number, since it is larger than the sum of its proper divisors (2389835).

81771878473 is a wasteful number, since it uses less digits than its factorization.

81771878473 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2389834.

The product of its digits is 14751744, while the sum is 61.

The spelling of 81771878473 in words is "eighty-one billion, seven hundred seventy-one million, eight hundred seventy-eight thousand, four hundred seventy-three".