81356723361 has 27 divisors (see below), whose sum is σ = 121467971313. Its totient is φ = 52471094760.

The previous prime is 81356723323. The next prime is 81356723381. The reversal of 81356723361 is 16332765318.

The square root of 81356723361 is 285231.

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

81356723361 is a `hidden beast` number, since 8 + 1 + 3 + 567 + 23 + 3 + 61 = 666.

It is not a de Polignac number, because 81356723361 - 2⁹ = 81356722849 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81356723381) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 26524950 + ... + 26528016.

Almost surely, 2^81356723361 is an apocalyptic number.

81356723361 is the 285231-st square number.

81356723361 is the 142616-th centered octagonal number.

It is an amenable number.

81356723361 is a deficient number, since it is larger than the sum of its proper divisors (40111247952).

81356723361 is an frugal number, since it uses more digits than its factorization.

81356723361 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6202 (or 3101 counting only the distinct ones).

The product of its digits is 544320, while the sum is 45.

The spelling of 81356723361 in words is "eighty-one billion, three hundred fifty-six million, seven hundred twenty-three thousand, three hundred sixty-one".