81090025 has 9 divisors (see below), whose sum is σ = 100607493. Its totient is φ = 64836000.

The previous prime is 81090011. The next prime is 81090041. The reversal of 81090025 is 52009018.

The square root of 81090025 is 9005.

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 22781529 + 58308496 = 4773^2 + 7636^2 .

It is not a de Polignac number, because 81090025 - 2¹⁵ = 81057257 is a prime.

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 8 ways as a sum of consecutive naturals, for example, 44125 + ... + 45925.

Almost surely, 2^81090025 is an apocalyptic number.

81090025 is the 9005-th square number.

81090025 is the 4503-rd centered octagonal number.

It is an amenable number.

81090025 is a deficient number, since it is larger than the sum of its proper divisors (19517468).

81090025 is an frugal number, since it uses more digits than its factorization.

81090025 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3612 (or 1806 counting only the distinct ones).

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

The cubic root of 81090025 is about 432.8351062102.

Multiplying 81090025 by its sum of digits (25), we get a square (2027250625 = 45025²).

81090025 divided by its sum of digits (25) gives a square (3243601 = 1801²).

The spelling of 81090025 in words is "eighty-one million, ninety thousand, twenty-five".