81528709955625 has 45 divisors (see below), whose sum is σ = 147158732060769. Its totient is φ = 43481617470000.

The previous prime is 81528709955591. The next prime is 81528709955701. The reversal of 81528709955625 is 52655990782518.

The square root of 81528709955625 is 9029325.

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

81528709955625 is a `hidden beast` number, since 8 + 1 + 52 + 8 + 7 + 0 + 9 + 9 + 5 + 562 + 5 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 6391850860521 + 75136859095104 = 2528211^2 + 8668152^2 .

It is a tau number, because it is divible by the number of its divisors (45).

It is not a de Polignac number, because 81528709955625 - 2²⁷ = 81528575737897 is a prime.

It is an unprimeable number.

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 44 ways as a sum of consecutive naturals, for example, 677139180 + ... + 677259570.

Almost surely, 2^{81528709955625} is an apocalyptic number.

81528709955625 is the 9029325-th square number.

81528709955625 is the 4514663-rd centered octagonal number.

It is an amenable number.

81528709955625 is a deficient number, since it is larger than the sum of its proper divisors (65630022105144).

81528709955625 is an frugal number, since it uses more digits than its factorization.

81528709955625 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 240808 (or 120399 counting only the distinct ones).

The product of its (nonzero) digits is 544320000, while the sum is 72.

The spelling of 81528709955625 in words is "eighty-one trillion, five hundred twenty-eight billion, seven hundred nine million, nine hundred fifty-five thousand, six hundred twenty-five".