81622775809 has 3 divisors (see below), whose sum is σ = 81623061507. Its totient is φ = 81622490112.

The previous prime is 81622775789. The next prime is 81622775813. The reversal of 81622775809 is 90857722618.

The square root of 81622775809 is 285697.

It is a perfect power (a square), and thus also a powerful number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in only one way, i.e., 780364225 + 80842411584 = 27935^2 + 284328^2 .

It is not a de Polignac number, because 81622775809 - 2⁷ = 81622775681 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 81622775809.

It is not an unprimeable number, because it can be changed into a prime (81622775209) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 142849 + ... + 428545.

It is an arithmetic number, because the mean of its divisors is an integer number (27207687169).

Almost surely, 2^81622775809 is an apocalyptic number.

81622775809 is the 285697-th square number.

81622775809 is the 142849-th centered octagonal number.

It is an amenable number.

81622775809 is a deficient number, since it is larger than the sum of its proper divisors (285698).

81622775809 is an frugal number, since it uses more digits than its factorization.

81622775809 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 571394 (or 285697 counting only the distinct ones).

The product of its (nonzero) digits is 3386880, while the sum is 55.

The spelling of 81622775809 in words is "eighty-one billion, six hundred twenty-two million, seven hundred seventy-five thousand, eight hundred nine".