81617728825 has 12 divisors (see below), whose sum is σ = 102208026348. Its totient is φ = 64647704000.

The previous prime is 81617728811. The next prime is 81617728901. The reversal of 81617728825 is 52882771618.

It can be written as a sum of positive squares in 6 ways, for example, as 95481 + 81617633344 = 309^2 + 285688^2 .

It is not a de Polignac number, because 81617728825 - 2⁵ = 81617728793 is a prime.

It is a super-2 number, since 2×81617728825² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is an unprimeable number.

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 11 ways as a sum of consecutive naturals, for example, 16159402 + ... + 16164451.

It is an arithmetic number, because the mean of its divisors is an integer number (8517335529).

Almost surely, 2^81617728825 is an apocalyptic number.

It is an amenable number.

81617728825 is a deficient number, since it is larger than the sum of its proper divisors (20590297523).

81617728825 is a wasteful number, since it uses less digits than its factorization.

81617728825 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 32323964 (or 32323959 counting only the distinct ones).

The product of its digits is 3010560, while the sum is 55.

The spelling of 81617728825 in words is "eighty-one billion, six hundred seventeen million, seven hundred twenty-eight thousand, eight hundred twenty-five".