81000090000025 has 81 divisors (see below), whose sum is σ = 121019987278749. Its totient is φ = 53621597789760.

The previous prime is 81000090000013. The next prime is 81000090000079. The reversal of 81000090000025 is 52000009000018.

The square root of 81000090000025 is 9000005.

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

It can be written as a sum of positive squares in 4 ways, for example, as 1113390059929 + 79886699940096 = 1055173^2 + 8937936^2 .

It is not a de Polignac number, because 81000090000025 - 2⁵ = 81000089999993 is a prime.

It is a super-2 number, since 2×81000090000025² (a number of 29 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (25).

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 80 ways as a sum of consecutive naturals, for example, 9135000642 + ... + 9135009508.

Almost surely, 2^{81000090000025} is an apocalyptic number.

81000090000025 is the 9000005-th square number.

81000090000025 is the 4500003-rd centered octagonal number.

It is an amenable number.

81000090000025 is a deficient number, since it is larger than the sum of its proper divisors (40019897278724).

81000090000025 is an frugal number, since it uses more digits than its factorization.

81000090000025 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17816 (or 8908 counting only the distinct ones).

The product of its (nonzero) digits is 720, while the sum is 25.

81000090000025 divided by its sum of digits (25) gives a square (3240003600001 = 1800001²).

The spelling of 81000090000025 in words is "eighty-one trillion, ninety million, twenty-five", and thus it is an aban number and an uban number.