81930358268521 has 9 divisors (see below), whose sum is σ = 95306816997399. Its totient is φ = 70225967063784.

The previous prime is 81930358268519. The next prime is 81930358268527. The reversal of 81930358268521 is 12586285303918.

The square root of 81930358268521 is 9051539.

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

It can be written as a sum of positive squares in only one way, i.e., 12091510971225 + 69838847297296 = 3477285^2 + 8356964^2 .

It is not a de Polignac number, because 81930358268521 - 2¹ = 81930358268519 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 81930358268521.

It is not an unprimeable number, because it can be changed into a prime (81930358268527) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 62714235 + ... + 64007311.

Almost surely, 2^{81930358268521} is an apocalyptic number.

81930358268521 is the 9051539-th square number.

81930358268521 is the 4525770-th centered octagonal number.

It is an amenable number.

81930358268521 is a deficient number, since it is larger than the sum of its proper divisors (13376458728878).

81930358268521 is an frugal number, since it uses more digits than its factorization.

81930358268521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2586168 (or 1293084 counting only the distinct ones).

The product of its (nonzero) digits is 24883200, while the sum is 61.

The spelling of 81930358268521 in words is "eighty-one trillion, nine hundred thirty billion, three hundred fifty-eight million, two hundred sixty-eight thousand, five hundred twenty-one".